RF: data fitting functions now using least-squares instead of minimisation

also updated tests
should be more robust and much faster (not iterative and no local minima)
ENH: a bugfix to val2array to handle single-val cases better

(tagged as ENH because it fixes a bug in unreleased code)

Was causing shape stimuli not to work in two ways:
1) couldn't handle the fact that the init value of the vertices had been
set as a list rather than array (now fixed during the creation)
2) couldn't handle a singular value because len(np.array(1)) gives error

Solution:
Test for None option first and then immediately convert to np.array.
(should we use asarray instead?). Then test for singular vals using
np.product(value.shape). Seems safer than all other options.
Merge branch 'master' of github.com:psychopy/psychopy
ENH: fixed the visual test bugs caused by new attribute setters

NB This is labelled as ENH because the bug it fixes in unreleased code
ENH: test_fitFunctions shouldn't be plotting for automated tests
TESTS: further psychopy.visual testing
ENH: trying some changes to app quit(), partly to quit in a more resilient way

and partly to allow testing to call app.quit()
ENH: App does not redirect stderr/stdout during tests (using arg commandline arg testMode)

also v minor change to changelog
tests: radialstim on linux is now effectively set to xfail (very low thresh)
TESTS: new error introduced in test suite
TESTS: sitll hadn't made the threshold relaxed enough to pass on the travis box
RF: fix some var names to be camelCase in experiment.py; docstrings

minor RF & doc fixes in Namespace
makeValid - remove add_to_space option (was unused)
Merge branch 'master' of git://github.com/psychopy/psychopy

# By Jon Peirce (6) and Jonathan Peirce (4)
# Via Jon Peirce (1) and Jonathan Peirce (1)
* 'master' of git://github.com/psychopy/psychopy:
  TESTS: sitll hadn't made the threshold relaxed enough to pass on the travis box
  TESTS: new error introduced in test suite
  tests: radialstim on linux is now effectively set to xfail (very low thresh)
  ENH: App does not redirect stderr/stdout during tests (using arg commandline arg testMode)
  ENH: trying some changes to app quit(), partly to quit in a more resilient way
  TESTS: further psychopy.visual testing
  ENH: test_fitFunctions shouldn't be plotting for automated tests
  ENH: fixed the visual test bugs caused by new attribute setters
  ENH: a bugfix to val2array to handle single-val cases better
  RF: data fitting functions now using least-squares instead of minimisation

Conflicts:
	docs/source/changelog.rst
  --> changelog conflict resolved by selecting upstream. mergetool prompted
      for what line-ending to use since the files differed.