(#2103) - fix websql changes() typo

Also removes the DOC_STORE.seq column,
since it actually wasn't being used.
(#1918) properly destroy leveldbs with prototype
(#2090 #2091) - update docs for 2.2.0
(#2104) - fix readTransaction on sqlite plugin
(#2073) - lets not filter based on an error here
(#1830) - fix browserifiablity
(#2027) - Blog post introducing persisted map/reduce
(pouchdb/mapreduce#145) - fix es3ify path

Apparently mapreduce can find es3ify now.
(#2067) - Update mapreduce dependency
(#2117) - Release notes for 2.2.0 release
(#2117) - Bump prerelease version
(#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
(#2023) - don't save revisions of local docs