Language-tool-python

- Support client-server model via setting the host to `0.0.0.0`. This allows many LanguageTool clients to connect to a single LanguageTool server. Inspired by feature requests, including 40 - thanks!
- Perhaps more importantly, finally adding support for the many options available in the [HTTPServerConfig](https://languagetool.org/development/api/org/languagetool/server/HTTPServerConfig.html). This enables lots of things: caching (both example-based an pipeline-based), custom language models, interfacing with premium mode, warming up the server, and more. Thanks to those who posted relevant issues, especially #50.

See the README for information on configuring a client-server setup or passing configuration options to LanguageTool.

language_tool_python` version 2.6.4 includes the following improvements:
- Upgrade to LanguageTool software version 5.6 (see 5.6 release notes here: https://github.com/languagetool-org/languagetool/blob/master/languagetool-standalone/CHANGES.md)
- Better information about killing java process (re 38) - add information to README about using `with .. as tool` and `tool.close()` to manage processes
- Better unit test coverage to confirm java processes are properly killed
- Removed some legacy code
- PR 51: Better support for the `'auto'` tag in LanguageTool (thanks minoguep)
- PR 46: Add requirements.txt to manifest (thanks dcbaker)

Also, we **dropped support for Python 3.5**, hopefully this doesn't affect anyone too drastically. This was necessary to add typing hints to our code, which hopefully is worth it!

LanguageToolPython 2.6.1 upgrades our LanguageTool version to 5.4, which gives us the main benefit of all of the [additional error detection rules](https://dev.languagetool.org/languages) added to LanguageTool 5.4 across the many languages LanguageTool supports.

Behind the scenes, I cleaned up the code a bit, and changed our web requests to use the [Python requests library](https://docs.python-requests.org/en/latest/) across the board. There had still been some legacy code that made calls to the raw urlopen() python binding, which caused various issues (such as #42) and was generally persnickety. Hope this works better!

Our most recent release updates to the [LanguageTool 5.2 release](https://forum.languagetool.org/t/ann-languagetool-5-2/6465) and makes some important bug fixes behind the scenes. Thanks RafaelWO, aokellermann, and misrasaurabh1 for contributing!

The main change in v2.4.0 is to support LanguageTool's [5.0 update](https://forum.languagetool.org/t/announcement-languagetool-5-0/5838/2), which supports more languages and errors.

Also made some miscellaneous changes:
- remove dependencies we don't need anymore and other stale things (`Dockerfile`)
- fix 'JDK 14 could not be parsed' issue
- fix enable/disable spellchecking features
- correct `Match` types with `utils.correct()` functionality (and add to README)