Starling-theme

- Add fix for left-padding in breadcrumbs c/o Harsha Kokel

TL;DR: :pencil2: Transferring repository from ``batflyer/starling_theme`` to
``starling-lab/starling-theme``.

This patch is being applied to finalize the move from ``github.com/batflyer/starling_theme``
to ``github.com/starling-theme``. The rename is done to ensure that names are consistent
between the package hosted on PyPi and the name associated with the GitHub repository.

Since the imported package uses underscores (in accordance with Python's syntax
requirements), the source folders will still use the ``starling_theme`` convention.

This mainly affects the ``setup.py`` script, with minor tweaks to hyperlinks and directions
in the associated documentation (specifically the ``README.rst``,
``documentation/source/developer_guide/01_development_environment.rst``,
``documentation/source/index.rst``).

TL;DR: This is a patch 🔖 for how the search bar is displayed (but actual search functionality is still broken).

Layout Changes 🚧

* Incremental work on fixing the search bar. This resolves the problem with displaying the search bar when the "search icon" is clicked; but there are still some jQuery errors which prevent the search results from actually being returned to the user.
* Incremental work on updating the color scheme. This adds a block comment to the ``theme.css`` including the color scheme Gautam used in the blue logo.

Dependencies ⬆️

* Adding ``starling_theme`` and ``sphinx`` to a ``requirements.txt`` file in the documentation directory. This is mainly to make it explicit that both need to be installed before the documentation is built, and because some documentation build services default to checking ``requirements.txt``.

README Updates 📝

* Adding image of the built documentation index to help illustrate what this package actually does. Added to README.
* Fixing some indentation problems with the code blocks.
* Setting the project state to "alpha".
* Current goals and open problems now lists a link to the project issues page.

TL;DR: This fixes a bug in the ``theme.css``, removes some text which was previously commented out, and adds documentation to this documentation.

``theme.css``:

* Some of the .css was originally brought over from the ``sphinx_rtd_theme``, but was commented out in ``0.1.0``. This has been removed.
* The Table of Contents along the left of the screen (which scrolls with the user) had a bug where the ``.current`` class was set to use ``font-weight: 900``. In reality this should have been ``a.current``, and has now been corrected in order to only bolden the current page's link.

General Documentation changes:

* Changelog is now part of the documentation, and is stored under: ``documentation/changelog/``.
* New ``.. toctree::`` for the main ``index.rst`` containing links to other relevant pages (in this case the GitHub and PyPi pages).
* ``source/index.rst``: Removed the part of the guide which suggested deleting the ``html_sidebars`` dictionary from ``conf.py``. This variable is necessary for the alabaster theme but it does not effect ``starling-theme``; so including directions to remove it was unecessary.

User Guide:

* Guides on environment setup and downloading contain discussion on how to get started from a user's perspective.
* An example for using ``sphinx-quickstart`` and switching out the ``conf.py`` variables to use ``starling-theme`` are now included.

Developer Guide:

* **Development Environment**: Contains discussion on creating an Anaconda environment for developing the theme.
* **Cloning from GitHub...**: Contains discussion on cloning the repository from GitHub and installing a development build using ``setup.py``.

* Table of Contents:
- `layout.html` and `theme.css` adjusted to create a static
Table of Contents that follows along the left side of the
page as the user scrolls down.
- This collapses into a drop-down menu in mobile view.
* `theme.conf`:
- includehidden = True
- navigation_depth = 4
* Search:
- Search bar is currently placed at the top of the screen.
- Default text replaced with "Search project documentation"
to help prevent it being mixed up with site-wide search.
* Documentation:
- `conf.py` imports version information directly from
`starling_theme.__init__`
- `index.rst` set to have hidden table of contents (now that
the actual Table of Contents is resolved).

* Header menu: Added the magnifying glass symbol back (by updating layout.html).
* `search.html` and `searchbox.html` added for searching the documentation.
* `theme.css`: Breadcrumb navigation and table-of-contents entries are now displayed properly.