updated installation, usage & modules docs -- cleanup with flake8
added support for "headers" command to display column number
associated with header names
added support for "headers" command to display column numbers
associated with header names
Merge branch 'feature/show_headers' into develop
updated to version 0.1.6
Merge branch 'release/v0.1.6'

Conflicts:
	docs/installation.rst
	docs/usage.rst
	sq/__init__.py
	sq/cut.py
	sq/reader.py
	sq/sqx.py