Previewer cleanup

- Add Try/Except Statements to imports (bad but works)
Merge pull request #43 from alexschiller/feature/player_update

Previewer cleanup
Fix import in tasks.py
Catch ImportError in image/handler.py.

Allows ImageFileHandler to be used without PIL
Fix files path in previewer app
Add mildly useful error message if file can't be rendered
Remove unnecessary exception handling for registering ImageFileHandler
Merge pull request #46 from CenterForOpenScience/feat/fix-app

Feat/fix app
Move Pillow -> image/export-requirements.txt
Remove old examples file
That doesn't belong there
Template doesn't assume so much about how renderers are written
Rename test directory for docx module
Handle ImportError in docx module
One test file per module
Pygments is a render requirement
Add detect tests for code handler
CodeFileHandler handles import error
RstHandler handles import errors; organize tests
Remove deprecated/unnecessary files