ENH: Added TrialHandler support to ioDataStore

Standard psychopy TrialHandler's can now be used to create a table in
the ioDataStore which can hold the values of trial rows as they are used
during the experiment. See
psychopy.iohub.client.ioHubConnection.createTrialHandlerRecordTable
method comments for usage example.

The ioHub ExperimentVariableProvider class should likely be deprecated
in favour of using psychopy's standard TrialHandler.
ENH: RatingScale can accept arbitrary response keys (new param)
TESTS: test ratingscale.py

- 86% coverage testing the init code, some .draw() coverage
- no added visual testing
TEST: RF test_ratingscale, ~95% coverage
Merge pull request #388 from jeremygray/master

ENH: RatingScale can accept arbitrary response keys (new param)
TEST improved testing of ratingscale.py

- 97% coverage, more asserts, use TEST_FONT
- minor tweaks to the ratingscale code to avoid bad values
Merge pull request #389 from jeremygray/master

TEST improved testing of ratingscale.py
TEST visual.helpers: contains(), .overlaps()

- 100% coverage of contains() overlaps() if you test using matplotlib 1.2+
Merge pull request #390 from jeremygray/master

TEST visual.helpers: contains(), .overlaps()
TEST visual.bufferimage.py

- 90% coverage, but almost no testing of actual function
- miss coverage for useShaders = False
TEST:  test_web (new under test_misc/)

- get 68% coverage if have internet access; skip tests if no internet access
BF: _getRegionOfFrame in pygame; closes #392
DOC: Fixed paths to images for case sensitive platforms.
DOC: Fixed warnings from sphinx and corrected two links.
DOC: Included missing file in documentation and corrected syntax.
DOC: Fixed warnings from sphinx in doc strings.
DOC: Fixed typos, syntax and minor errors in documentation.
DOC: Updated examples in doc strings not to import deprecated log module.
Merge pull request #393 from philippwiesemann/master

DOC: Fixed typos, sphinx warnings and minor errors in documentation.
BF: fixed buglet in new data handling method for StairHandler