Fix #370, fix session saving from the control panel
Use the isSavable() of session manager to determine whether a notebook
is savable. And if so, beaker will just save it with the 'overwrite'
flag turned on.
Please note that with this change, for the sessions that are not
savable (read-only or new notebook), we still don't have the nice
state machine from spec of #247 yet. #415 was logged for
implementing that.
Merge pull request #414 from twosigma/byu/plot

Merge after confirming `gradle check` passed
Merge pull request #418 from twosigma/alee/fix-370

Fix #370, fix session saving from the control panel
update bower from 1.2.8 to 1.3.8
Merge pull request #419 from twosigma/update-bower

update bower from 1.2.8 to 1.3.8
Bump version of test lib

Lots of new features to make debugging and writing much easier
https://github.com/mojotech/pioneer/blob/master/changelog.md
Merge pull request #420 from twosigma/sjs/update

Bump version of test lib
Merge remote-tracking branch 'origin/master' into byu/plot