Add logging to save item
Update `requests` library to 1.2.3
Use oauthlib directly for LTI module
Improve accessibility of forums navigation elements

The home icon and discussion topic drop-down icon now have text that is
visible only to screen readers. The visual change between the icon and the
topic name with down-arrow is now achieved with the CSS visible property
instead of the opacity property, so only one at a time will be visible to
screen readers as well as visually.
Pass hostname to LTI XModule

Necessary for RFC compliance with oauthlib
Remove some cruft from forums SASS
Response.json is now a callable
Add default launch url for lti.
Merge branch 'db/update-requests-lib' of github.com:edx/edx-platform into db/update-requests-lib
Stub headers if scheme not provided.
Merge pull request #931 from edx/jkarni/fix/itemsavelogging

Add logging to save item
reformat for readability
Merge pull request #921 from edx/gprice/forum-nav-accessibility

Improve forums nav accessibility
Merge pull request #880 from edx/db/update-requests-lib

Update `requests` library to 1.2.3