#652 - Fix for PP error when SlideShare urls contain querystring params

Brought in the SlideShare module which will take care of the querystring stripping
Temporarily pointing to my (@simong) repo in package.json till the fix
gets merged upstream.
fix outdated preview image on activity feed
lock on externalId when creating new users
add test for account creation locking
simplify logic flow, fix error message
#663 - Fix intermittent failure when importing users.
#664 - TincanAPI test failure fixes

* Replaced switch-case with if-elseif
* Fixed up unit tests by forcing collection before the tests
add revision back to the content body modified event
add unit test
Renamed `done` callback function in importUsers
Merge branch '664-tincan-failures' of https://github.com/simong/Hilary into 664-tincan-failures
Documentation improvements
Merge branch '652-slideshare-links' of https://github.com/simong/Hilary into 652-slideshare-links
Documentation changes and re-ordering of slideshare import
Merge pull request #621 from stuartf/activityPreviews

Activity shows old preview in activity stream after new revision has been uploaded
Using an in-memory index and 0 replicas for elasticsearch when running the unit tests.
allow express to accept POSTs up to the limit we set in nginx
move max upload size setting to config.js
check the output of both user creations when testing for race condition
Added jsdoc and assertion for double failure to account creation locking unit test