Merge pull request #112 from lev-kuznetsov/master

Null check
Added frontend for annotation buttons
Merge remote-tracking branch 'origin/master' into fix-issue-107
Cleaned up buttons. fixes #107
Fixed Heatmap overlay
Merge pull request #113 from jfarid27/fix-issue-107

Fix issue 107
Cleaned up logging a little bit; proper cleanup on matrix data. There's
still the issue of loading annotations.