Configurable popups, fixes #16

[msjyoo]

Hello!

I've implemented a bunch of options to make popups configuable and more user friendly. This also fixes the issue of popup texts being too cramped when they are long.

I've also changed the indenting of the settings file to four spaces, since that's what all the other plugins seem to use (including ST3 itself).

Please code review and merge. Thanks!

[msjyoo]

Maybe a command to toggle the popup message truncation like https://github.com/bblanchon/SublimeText-HighlightBuildErrors/commit/75e29a1e0f651e94412a5249f471be85c274fce6? But I don't think it's necessary.

[bblanchon]

Sorry for the long delay. I gave you push access to the repository, but if you prefer pull-request, we can continue this way.

Thanks again Michael!

[msjyoo]

@bblanchon Thanks!