Merge pull request #72 from yfcheung/master

Regression fix - 10 posts/topic
Additional conference email options

Issue #42:
* Selected attendees
* "From" field
* Additional JS for selection boxes
Modifications to Science Challenge for 2013 Minor Challenges
Changes to .gitignore
Changes to .gitignore
Removal of now obsolete library file in smsglobal.c
Correct static path to email attachments

Fix for static path in new AWS server set up
Force HTML mode for volunteer invite emails

By default, the email is encoded in HTML anyway (:271), so this should
be active.