Improve URL detection in YouTube plugin
Add command response to YouTube plugin, fix #43
Escape HTML entities in twitter plugin, fix #44
Add Vimeo plugin, fix #42
Add instagram plugin, fix #41
Merge branch 'master' into next-gen
Remove double newline on .gitignore
Update unit tests to match correct behaviour
Add Instagram and Vimeo plugins from master
Improve code formatting
Rename websites plugin to url_titles
Change url_titles plugin to use a handler system
Move YouTube URL detector into URL titles plugin
Move Vimeo URL detector into URL title plugin
Move Instagram URL detector into URL title plugin
Remove handler subsystem

No longer necessary and will be redesigned in next-gen branch.
Merge branch 'master' into next-gen