Fix wrong assertion in client_tests

The client-test test_get_mapping expects a value of 'yes' for the
'store' property. However, the value returned is True, not 'yes'.

This changes the test case accordingly.
Use six string_types in isinstance
Remove the info() routine for now so master is releasable again. Ref #111.
Bump version to 0.6, and slap a date on the release notes.
Patch up a test failure.

We really have to do something about our tests and the inconsistent behavior of ES from version to version.
Travis CI doesn't use the "secure." subdomain anymore, and linking there causes a redirect to an invalid URL.
Clarify in release notes that the bulk_index bug was ES-version-specific.
merge konrad's fixes for the client_tests
merge with upstream

0.6 has been released, so it's a good time to merge.