Add JSON import/export. Closes #25. Closes #30.

Jobs can now be imported/exported to and from JSON in the
jobs view. This is cross-compatible; jobs from a Mongo-backed
Dagobah can be imported into a SQLite-backed Dagobah
and vice versa.
Stop using mirrors from pip, it's breaking Travis for some reason
Remove some outdated stuff at the end of the readme
Working towards addition of better remote host management
Merged from patent with importexport feature