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.
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
Change course id limit to 65.

STUD-726
Remove dogstatsd-python in favor of dogapi

Also added datadog application to commom django apps and set it to use
a local statsd server by default.
Updating LTI Jasmine tests.

Due to the fact that by default the LTI settings have "http://www.example.com"
set as the default form action (launch_url), tests were updated to reflect the
fact that when setting is in default state, form is not submited, even when
the form action is not empty.
Merge pull request #943 from edx/valera/update_lti_tests

Updating LTI Jasmine tests.
Merge pull request #928 from edx/christina/courseid_length

Change course id limit to 65.
change formatting for email messages to use full_name instead of first_ and last_name

fix templates
fix tests
Merge pull request #905 from rocha/datadog-statsd

Remove dogstatsd-python in favor of dogapi