:lipstick: Move helper
Add click and shift-click in gutter
Handle dragging in the gutter

Including shift-click dragging better than the old editor!!!!!!
Throw error when no animation frame was requested
:lipstick: Break out separate methods for gutter click and shift-click
Fix spec
Select to the end of the last row rather than beginning of row + 1
Revert "Select to the end of the last row rather than beginning of row + 1"

This reverts commit c5815d2af9e712d6a574aecd1b5f121e8b8b3c42.
Merge pull request #2665 from atom/bo-gutter-selection

Implement gutter clicking and dragging to change selection on react editor