Implementing __rpow__

See merge request !58

Update compyte for strides on zero-sized arrays

See merge request !57

Implementing stack() and concatenate()

See merge request !56

docs: fix a few simple typos

There are small typos in:
- aksetup_helper.py
- examples/from-wiki/mandelbrot_interactive.py
- pycuda/cuda/pycuda-helpers.hpp
- test/test_gpuarray.py

Fixes:
- Should read `subtraction` rather than `substraction`.
- Should read `support` rather than `supprt`.
- Should read `right` rather than `rigth`.
- Should read `preferred` rather than `prefered`.

Closes #294

Update dev attr

See merge request !55

Fix a py2-ism in the tutorial

Update compyte

See merge request !54

Run flake8 in Github CI on target Py version

Drop dependency on decorator module

See merge request !53

Update mempool to version from PyOpenCL

See merge request !52