for code review issues

Feature/ichuang/update symmath server

Merge pull request #1227 from MITx/feature/ichuang/fix-capa-contextualize-text-for-option-response-and-mc

fix capa to add contextualize_text for optionresponse and multiplechoice

Fix parent lookups when the same named tag exists in multiple courses

The parent trees are built on a per-course basis (so it'll throw ItemNotFoundError
if an item exists in a different course from the one you're asking after. NoPathToItem
can still happen with MongoDB backed courseware. They store things like the info page
as HTML snippets which are orphaned from other content.

Clarify the syntax of the rake fasttest command

Clarify that you need to start up the mongo daemon

Fix typos in job and faq pages

Signed-off-by: Carlos Andrés Rocha <rocha@edx.org>