use IORef instead MVar in debugBufferContent

Should fix 7.6.3
Update changelog.
Bump version to 0.10.
Bump yi-language version.
make License field cabal2nix-friendly
Include test files + minor cabal fixes
export {get,set}Dynamic from Yi.Editor

I was using those in my config.
Actually, {put,get}EditorDyn are exported

TODO: remove {set,get}Dynamic and friends from Yi.Editor.Internal
Remode dead module.
Disable magical autoindent when removing rectangular blocks.
Disable autoindent when editing with multiple cursors.
Install libicu-dev.
Handle more encodings.

Fixes #638
Start new version in the changelog
Temporarily disable 7.6.3

https://github.com/Aelve/charsetdetect-ae/issues/1
Reflect possibility of failure in editFile's type
s/withCountOnBuffer0/withCountOnBuffer/
Fix :q behavior on last window.

Quitting the last window is actually quitting the editor, so make :q
equivalent to :qa if there is only one window and only one tab, thus
forcing all of the required checks on hidden buffers being saved to
actually occur.

Closes #562
Fix cursor positioning in vty.
Accept <C-m> as <CR> in vim ex mode even with pango frontend.