(#906) - Added cordova unit test runner
(#906) - Cleanup and move cordova tests

Cordova tests are now in tests/cordova, and
instructions are in the main CONTRIBUTING.md.
(#2119) - Update level-js dependency
g(#1661) - use task queue for IDB for IE

gAdds a task queue for all create/destroy
goperations on IDB databases, because apparently
gIE 10 and 11 can't function correctly if there's
gany overlap between any destroys/creates (even
gfrom different databases).

gAlso apparently you can't have two databases
gwith the same name open at the same time,
gso we have to cache this.  Unfortunately,
gChrome prefers the opposite, so for the time
gbeing I'm using user agent sniffing to
gexclude Chrome from the caching.  If anyone
gcan think of a better idea, I'm all ears.