WIP: new example with real-time digital signals
ncols and nrows are now variables.
Implemented GLSL-based clipping in the fragment shader.
Added static and dynamic buffers for position in real time signals example.
Merge pull request #340 from rossant/realtime-signals-example

WIP: new example with real-time digital signals
Fixed bug on real time demo with Intel GPU.
Merge pull request #342 from rossant/fix-realtime-signals

Fixed bug on real time demo with Intel GPU.
FIX: Fix color test
Merge pull request #343 from Eric89GXL/fix-colors

FIX: Fix color test
Run tests with same interpreter that launched test

This makes the tests on the backends run with the same
Python interpreter used to launch the test. i.e. when I do
`python3 make test pyside`, the tests should be done in
Python3, not Python2.
Minor updates in README.
Merge pull request #344 from almarklein/test-use-right-python

Run tests with same interpreter that launched test