Wenv

- FIX: CI tests failed due to dependency issue in Python 3.4, see issue 13.

- FEATURE: `wenv init` can be used offline. A cache for installation files was added, see 1. `wenv cache` fills the cache automatically (internet connection required), `WENV_OFFLINE=true wenv init` runs the initialization of the actual *Wine Python environment* offline. Offline functionality can be configured through the new configuration parameters `prefix`, `offline`, `cache` and `packages`. See 1.
- FEATURE: Added new configuration parameter `wineinstallprefix` allowing custom wine installation paths, see 10.
- FEATURE: `wenv` now not only exposes `python.exe` but also `pythonw.exe`.
- FEATURE: New APIs: ``Env.install_package``, ``Env.uninstall_package``, ``Env.list_packages``
- FIX: Using `requests` instead of `urllib` for loading components. Removed `certifi` workaround.
- FIX: For user installations, `sys.prefix` is not the right place to put shared resources. `site.USER_BASE` should be used instead, see 4.
- FIX: `wenv init` would trigger Wine's "update prefix" message window even when used in scripts. Now suppressed, see 5.
- FIX: `wenv pip` does not warn anymore that exe-files are not in PATH, see 6.
- FIX: `wenv help` only shows `python` command if the Python interpreter is actually available.
- API: Environment class is exported as ``Env``. ``env`` is deprecated and will be removed.
- API: The constructor of the environment class expects keyword arguments matching configuration options. The use of a ``parameter`` dictionary is deprecated and support will be removed.

* FIX: `wenv` installed its environment into `shared` folder instead of `share`.
* FIX: Broken links in README.md

`wenv` broken out of [`zugbruecke`](https://github.com/pleiszenburg/zugbruecke) and turned into an independent package. The following changes were made since `zugbruecke` 0.0.14.

| **OLD** | **NEW** |
| ------------------------------------- | ---------------------------------- |
| `wine-python` | `wenv python` |
| `wine-pip` | `wenv pip` |
| `wine-pytest` | `wenv pytest` |
| `!/usr/bin/env wine-python` | `!/usr/bin/env _wenv_python` |

- Initial release


How to release `wenv`

1) Merge all relevant changes into branch `develop` - this is where development and pre-release testing happens.
1) In branch `develop`, run tests and examples and check that the documentation builds without errors: `make test`
1) In branch `develop`, add missing changes to `CHANGES.md` and commit.
1) Push branch `develop` to GitHub: `git push origin develop`
1) Wait for feedback from CI.
1) Change to branch `master`: `git checkout master`
1) Merge branch `develop` into branch `master` (comment `f"{version:s} release"`).
1) Push branch `master` to GitHub.
1) Tag branch `master` with `f"v{version:s}"`: `git tag "v0.0.1"`
1) Push the tag to Github: `git push origin --tags`
1) Build and sign packages: `make release`
1) Upload package to `pypi`: `make upload`
1) Change to branch `develop`: `git checkout develop`
1) In branch `develop`, bump the package version in `src/wenv/__init__.py` by changing the `__version__` string.
1) In `CHANGES.md`, indicate that a new development cycle has started.
1) Commit to branch `develop`.
1) Push branch `develop` to GitHub: `git push origin develop`