Print file count before and after tests in travis.
Move open file count to right after `dacluster start`
Add a decorator for protocol validator functions.

Wrapped functions throw an exception rather than returning a success value.
Use the exception thrower in our DAP testing.
Remove an unused import.
Return the validator tuple on success.

Because why not?
Merge branch 'master' into feature/exception-throwing-protocol-validator
Merge pull request #327 from cowlicks/open-files

Print file count before and after tests in travis.
Context's now put thier keys in a dict.
Fix rebase conflict.
Add simple tests for DAP validator wrappers.

Incidentally, add the test file `distarray/tests/test_testing.py`.
Merge pull request #329 from enthought/feature/exception-throwing-protocol-validator

Wrappers for DAP validator functions that throw exceptions
Merge pull request #315 from cowlicks/Namespaces-are-one-honking-great-idea

Refactor key-management
Put client side modules in distarray/client/ and change imports.
move client.py -> distarray.py and change imports to reflect this.
move DISTARRAY_BASE_NAME into top level __init__.py

This is because dacluster should not have to impor distarray/client/ to
clean things up.
Fix circular import issue with distarray.py
client_maps.py -> maps.py. add __future__.absolute_import where needed.

Since the module distarray/client/distarray.py's name conflicts with the
package name we import `absolute_import` everywhere in the file.