edx.org: adds in variables/mixins to support edx.org visual changes
edx.org: applies edx.org visual changes (with overrides/new mixins)
edx.org: handles letter-spacing on buttons
edx.org: revises iframe-based register/status buttons to match revised styles
edx.org: revising base link color variable to use darker value for accessibility
edx.org: abstracting new edx.org  button extends and colors with other themes in mind
Merge remote-tracking branch 'origin/release' into rc/2013-07-30
Merge branch 'master' into rc/2013-07-30
Reverting 89c48f4a3047 to unbreak codejail for this release.
Merge branch 'master' into rc/2013-07-30
Make sure that all tab types used by the default for the course.tabs field work correctly
Merge pull request #524 from edx/cale/external_discussion_tab

Cale/external discussion tab
fix for underscore template issue for xmodules
removing an unneeded line that does damage
changing the default in common.py
Merge pull request #530 from edx/e0d/fix_feature_flag

E0d/fix feature flag
make user_api compatible with HTTP basic auth
Merge pull request #531 from edx/hotfix/jsa/user_api_basic_auth

make user api work with basic auth
Merge branch 'release'