Merge pull request #169 from lexa/master

"Undo" after leaving mc mode will restore cursors as they was
Add @lexa to list of contributors
Consolidate contributor entries for Aleksey
Add function to disable mc undo into undo-list.

When user enables mc mode we need to add function to disable mc mode
into undo-list. When users starts to hit 'undo' at some point mc-mode
will be disabled.