Overlay refactoring.
Implement :sort and ranges.

:sort mainly serving as a way to test the ranges.

Fixes #694.
Fixes #695, at least partially by implementing the parser.
Added dynamic compilates and tags/TAGS to .gitignore.
HLint cleanups.
Merge pull request #701 from mgajda/Cleanups

Hint and warning cleanups
Proposal for our own HLint rules
FIXED: Home/End/PageUp/PageDown in insert mode work.
Added :undo to Vim Ex mode.
Completion for Ex command 'undo'.
Vim keymap : poor-man's <C-w>←↑→↓ with prevWinE/nextWinE
Vim bindings for changing layout managers.
Vim :help shows all funs in scope, or type of a named fun.

Note that if you want more than just a type of a binding,
you might use ctags index over Yi documentation,
after examining the help index.
Merge pull request #703 from jhance/sort

Implement :sort and ranges.
Fix Haddock syntax
Remove unnecesary parens.
Merge pull request #704 from mgajda/HLint

Proposal for our own HLint rules
Merge pull request #702 from mgajda/Features

Vim keymap fixes and additions, including undo and help
Bump version, update CHANGELOG.
Merge pull request #706 from mgajda/ChangelogAndVersionBump

Bump version, update CHANGELOG.
added CUA bindings for PageUp and PageDown keys