(#1658) - integrate persistent mapreduce

This commit ensures that the persisted map/reduce
indexes are destroyed when their parent database
is destroyed.
(#1818) - Tidy alerts
up version to 2.2.0-alpha
(#113) - Initial infrastructure for performance testing
(#1834) - More performance tests

Also updated CONTRIBUTING.md to explain how
to access performance tests.
(#1821) - Fix hotlink
(#1765) - Make npm run build-site rebuild css on less changes
(#113) - Ensure perf tests get build on first run (and tweak docs)
(#1752) - Scrollspy on side nav on api page
(#1533) - Reformat lines to be < 80 characters
(#1820) - add docs for persisted mapreduce

This includes documentation for two new API methods:
db.putView() and db.viewCleanup().