(#549) - documentation

Add also a word about running single test file in a browser.
Merge pull request #554 from neojski/single-test-files-docs

(#549) - documentation
allow single map function to query
fix bugs causing issues with multiple changes listeners on a single Pouch instance, fixes #559
test for issue #559
Resolved first commit
More tests for task queue
Resolved next commit
All tests but changes filter work
Resolved another commit
Define openTestAsyncDB
Fixed db.query test for taskqueue
Small nit fixes
Yield on destroying of pouch to eliminate race conditions
A few nit fixes
Mostly working except info. debug statements
Revert "Yield on destroying of pouch to eliminate race conditions"

This reverts commit 223f6a193d6af42141341a818fd43556d5fd5d68.
Delete database before test
Cleaned some code cruft
Use consistent naming. Switch job to task for task queue.