Fixes #372

Before attempting to send mail, the hostname is retrieved using
socket.gethostname. If the hostname includes 'microbio.me', then mail is sent.
Otherwise, the user is dumped back to the portal with a message stating that
mail can be sent only from the microbio.me domain.
Merge branch 'master' of https://github.com/qiime/qiime_web_app into i372
Add function can_send_mail

takes no arguments, returns true if 'microbio.me' is in socket.hostname();
returns false otherwise
Adding doc string and streamlined fn
Modify files to use can_send_mail

Files should use can_send_mail from utils.mail instead of explicitly checking
whether or not 'microbio.me' appears in socket.hostname() return value
Merge branch 'master' of https://github.com/qiime/qiime_web_app into i372

Conflicts:
	www/americangut/submit_human_survey.psp
Add better error catching on add_participant.psp
Merge pull request #451 from adamrp/i372

Fixes #372