Only using explicit namespace when deserializing key pb.

This issue surfaced during review for #282.
Adding checks for namespace in datastore helpers test.

This is to ensure that values are correctly ignored when
the field isn't set on the protobuf.
Merge pull request #292 from dhermes/unmarshall-key-namespace

Only using explicit namespace when deserializing key pb.
Makes operator checking deterministic in Query.filter.

The order of dictionary keys is not guaranteed between runs of
code so `expression`s ending in '>=' or '<=' were sometimes
matching for '='.
Adding test to make sure the correct operators get set on filter.
Using operator dict in datastore.query and splitting on whitespace.
Adding test for datastore.query.filter with no operator used.

This was to get test coverage back to 100%.
Merge pull request #294 from dhermes/query-operator-fix-dict-random-order

Makes operator checking deterministic in Query.filter.
Using custom Travis-built wheels when installing.
Making sure the wheels are rebuilt after a change to master.

Other changes
- Fixes the directory that the wheelhouse was in.
- Consolidates the merge check into merge.sh.
- Checks bash code for style with shellcheck.