Say `Contents API 5.7.4` instead of `Notebook v5` in notebooklist.
EIN doesn't care about the python version (2.7, 3.5) or the
ipython version (5.8.0, 6.2.1). The "jupyter notebook contents api"
version (currently at 5.7.4) is the thing that matters.
Coursera appears to kill websockets every minute or so, and I'm
observing firsthand the buggy behaviors described in #356. This PR
cleans up the websocket code and kernel restart logic. Removed
backwards compatibility for the v2 messaging api
as keeping it in the presence of the refactoring would make it more
broken that it already was.
Merge the login and open commands (open aliased to login). Add login
tests described in #352.
Attempt to improve user experience by synchronously executing
`ein:jupyter-server-start`. `ein:dev-prefer-deferred` custom variable
allows easy switch to compare sychronous versus old asynchronous behavior.
Use deferred and callbacks instead of `:sync t` for tkf requests which
is known to have issues. Query server attributes once on
notebooklist-open to avoid sequencing issue #176 (but allow Resync).
Under curl backend, a second request for the same "key" as a pending
request will abort the latter, which has resulted in a clobbered
curl-cookie-jar file, so merely warn and don't abort.
Fix#176
