Clanvas

* Change rcfile login method to use new clanvas config (similar to SSH config).
Usage instructions now located in [README](README.md).
* No longer run `~/.clanvasrc` file on startup.
* Add descriptions to tab completion. For example course completion now includes
course titles and assignment completion now includes assignment names.
* Save/load persistent `readline` history.
* Removed `requirements.txt` and `dev_requirements.txt`, the dependencies can be resolved
with `pip install -e .` and `pip install -e .[dev]`
* Set dependencies for `cmd2` and `canvasapi` to exact versions for stability.

* Fix bug which caused crash if no courses were associated with the account.
* Fix bug which caused crash if a course has no name.

* Change the default prompt colors to higher contrast.
* Make it easy to customize prompt colors by allowing `ESC` (`\x1B`) in the `prompt_format`
* Rename `prompt_string` to `prompt_format`
* Fix `pullf` which was totally broken by a change in the previous release. This is why adding more regression tests is priority!

* Fixes the version of `cmd2` to exactly `0.9.4` because of a bug that caused Clanvas to crash. This should be resolved in `0.9.6` of `cmd2`.
* Regression tests in the dev environment!

* Cleaned up tab-completion code and hooked in to some nice cmd2
argparse integration, now tab completes flags and gives hints
with descriptions.
* Added command `ua` for uploading submissions to assignments.
* Made `lc -l` not require an enrollment term ID since sometimes a
course object does not always exactly model a course.
* Removed usage of deprecated canvasapi functions which were spraying
warning messages all over the place.
* Add categories to the `help` command.
* Add bounds (major version) to cmd2 and canvasapi dependencies to avoid
random breaking in the future.

Added commands for navigating announcements.

| Command | Meaning |
|-----------|-----------------------|
| lann | list announcements |
| catann | print announcements |

* Fixed program crashing from a [cmd2](https://github.com/python-cmd2/cmd2) update