Setup for a png-based ipynb app backend

This is just the app stuff, but I think Kaftan already
has the rest more or less finished. If we combine the
two, we have an actual IPython backend!
ipynb app: we *can* be not available.
ipynb-app: fix style and not available
ipynb app: rename to ipynb_vnc
arg flake
ipynb app: dont use glut as a back-backend

This should prevent the stalling of Travis I hope
fix to last commit
Merge pull request #297 from almarklein/ipynb-app

Setup for a png-based ipynb app backend
Update read_pixels and its docstring
read_pixels returns 3D array of pixels.
When reading pixels we should also read the 'Alpha' values, so
instead of g.GL_RGB, we should use gl.GL_RGBA.
Fix test, have to compare with size + (4,)
Fix test, get rid of the alpha before testing
Update against PEP8
Flip the image before return
- In read_pixels, the result image is upside-down. Flip the image using `[::-1]`.
- Test for read_pixels
Flakification
No need to call `_vispy_warmup()`
Update flip with [::-1,:,:] instead of [::-1]
+ Fix typo
Fix typo
Add alpha toggle to `read_pixels`
Flatten namespace
Merge pull request #301 from mfkaptan/test-read-pixels

Flip the image in read_pixels and test read_pixels