Deprecate and finally drop Bower support

I think it’s time to deprecate support for Bower gracefully and eventually drop it completely in the next major release (3.0.0).

This is a topic that has been discussed a little bit in the past, but I always argued against it since we had users that preferred to use xterm.js via Bower.

Eventually I changed my mind after seeing the weird things that can happen with the built files checked out in the repo and reading https://github.com/codemirror/CodeMirror/issues/4328#issuecomment-255110880, which actually states the fundamental design issue of Bower: it confuses source repositories (like this) with distribution mechanisms.

To the point, I propose taking the following steps to make sure that this goes as gracefully as possible for our users:

1. Create a new xtermjs/bower repository, where we will point the xterm.js Bower package and push the built files of each release there (starting with the current one).
2. Remove dist from this repository completely, ignore it from Git and include it in NPM distributions
3. Stop updating the xtermjs/bower repository starting from version 3.0.0

/cc @Tyriar

[Greenek]

If anyone is looking for xterm.js>=3.0 in bower repo, you can use bower install --save xterm.js-next. It’s my fork created for personal use, but I try to keep it updated.

[Tyriar]

@Greenek thanks for taking that up! 😃