Get rid of Yi.Region import
Give the boot to lexers + Prototype
Merge branch 'master' into lexer-move
dep on fixed yi-language
Make GHCi process name a variable.
Small cleanup
Statically enforce Editor invariant + cleanup
Expose the GhciProcessName var to the user
Hopefully fix vim tests
Allow the user to set GHCi args too.
Catch failure when subprocess fails + clean up
Fix vim repeat feature for non-qwerty layouts.
Fix macro playback for non-qwerty layouts.
Expose GTK Window.

Closes #557. This is a cherry-pick + squash + update of what was given
in #557. The omitted commit was adding Window to the UI structure which
means we'd always have to build with Pango for Yi.UI.Common to compile
which is undesirable. An alternative solution would be to parametrise
UI by the window type.

Conflicts:
	yi/src/library/Yi/UI/Pango.hs
A little housekeeping
Fix :tabe<Tab> resulting in :tag.
Remove dead code.
Add -feventlog flag.
Eliminate idle CPU consumption of vty frontend.
Add -eventlog option only when necessary.