In light of #425 and #456, provide more guidance on curl errors.
Also, clean up eldoc stub. Leveraging elpy's eldoc perfection seems
the only sensible choice, however.
```
"http://localhost:8888"
"http://localhost:8888/"
"http://127.0.0.1:8888"
"http://127.0.0.1:8888/"
"8888"
8888
```
Ideally these should converge to the same thing. Since many hash
tables are keyed off `url-or-port`, forgetting to
normalize `url-or-port` with `ein:url` leads to missed cache hits and
general malaise. So we try to do that.
Address a FIXME: apply callbacks to `ein:notebook-list-login-and-open`.
Removed py3.5 from travis build matrix to reduce developer strain.
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
Basic, mostly untested support for the brave new world of IPython 2.0.
2.0 now supports the concepts of 'paths', letting notebooks be stored in
a directory hierarchy. This has resulted in a change in the web API -
most URL's are now prefixed with 'api/'.
EIN does not (yet) support hierarchical notebooks, but at least it now
plays better with the new URL scheme for iPython 2.0.
Oh, there also seems to have been a change in the format of the ipython
notebook. This has been fixed too, but is probably bakcwards
incompatible.
