Do not crash the program for second unbind().

Sometimes cleanup code will unbind() a session when the request
being made is complete. Sometimes the same cleanup code is ran
for a session that ended. It's okay to call unbind() -- just
make it a no-op.
Lock version numbers for Mocha, Jasmine, Expect.js.

Jasmine at master broke recently. Switching all of these
to the latest version tags available.