Document the build system interface used by pip
Fix compatibility with wheel 0.23.0

wheel now only produces the major python version for the tag of pure
distributions, so expect that instead.
underscore unused variables
Merge pull request #1703 from Ivoz/pep8fix

underscore unused variables
Merge pull request #1702 from Ivoz/wheel023

Fix compatibility with wheel 0.23.0
Merge pull request #1675 from pfmoore/docs_setup_py

Document the build system interface used by pip
Note `--build-option` only available in `pip wheel`

I got a little confused, per issue #1707.
Merge pull request #1709 from davclark/develop

Note `--build-option` only available in `pip wheel`
Add information about command line option

... which can be used with get-pip.py
Fix conjugation and line length
get-pip.py option examples
break out the examples so we can add a qualifying footnote for --user installs
Merge pull request #1711 from qwcode/get-pip_options

Document using get-pip options
Clean up gitignore