Disable the debugtoolbar icon on successful request

This gets in the way of the sidebar. It is possible to move it to
another location using debugtoolbar.button_style but there is nowhere
useful to put it where it doesn't get in the way.

Instead it can simply be loaded manually by visiting:

http://localhost:5000/_debug_toolbar/
Add a debugging section to the README

This introduces the debugtoolbar.
Remove debugtoolbar as a production dependency

We now install it as an extra requirement.
Merge pull request #1294 from hypothesis/debugtoolbar

Improve debug toolbar integration
Don't install dev dependencies in prod
Update CHANGES.txt
Add issue numbers to changelog
Remove unnecessary leading slash in asset base url
Change maintainer in setup.py to eng@hypothes.is
Tagging v0.1.0
Include dependencies for front-end unit tests

Using Karma, Angular Mocks, Chai and Sinon.
Add Karma test runner for frontend
Setup unit tests for the username directive

Also refactored the directive to remove the dependency on the
controller. The ng-model attribute is still required but only to set
the scope.
Removed unused asset output targets
Fix versioneer.versionfile_build
Bump versioneer to v0.11
Tagging v0.1.1
Remove unneccessary MANIFEST.in line
Update MANIFEST.in
Add missing author_email package metadata