Changing the Python files to PEP8 format. Line length 92.
Manual alignment fixes.
Further PEP8 fixes not caught by autopep8
Remove overriden property norm from Dat
Remove overriden property c_vec_dec from Arg
Add missing decorator import
Remove unused variables and imports
Add module level list of public objects defining the pyop2 API
Selectively ignore flake8 warnings
More PEP8/flake8 fixes for demos
More PEP8/flake8 fixes for unit tests
PEP8/flake8 fixes for regression tests
Flake8 fixes for setup.py
Add flake8 configuration to tox.ini
Add make target lint to run flake8 code linter
README update with flask8 testing dependency
Merge pull request #186 from OP2/pep8

* Convert all Python files to conform to PEP8.
* Remove unused imports and variables.
* Add a code linting test using `flask8`.
* 79 character line length is not enforced by the linter.