Fixed: generator and fixture set for new data format
Fixed: mailboxes were not recursively immutables
Removed:  is defined in the application router class
Removed: last references to the mailbox store
Fixed: account update didn't work anymore
Removed: remaining reference to MailboxStore
Removed: gulpfile (gulp not used anymore)
Fixed: mailbox dropdown was not showing all mailboxes
Upgraded: immutable
Fixed: the selectedMailboxID could not be set
Removed: unused code
Removed: mailbox specific code (now merged with accounts)
Merge pull request #12 from jsilvestre/master

Various fixes