Add missing css arg to the usage documentation
Merge pull request #36 from brad/patch-1

Add missing css arg to the usage documentation
Generalize the script to all icon fonts

- Add --font-class-prefix option to enable finding other font classes
- Add --x option to adjust x offset
- Add --y option to adjust y offset
- Error handling for icon character extraction
- Change script name to font-to-png.py
- Adjust README with new usage options
add information about python dependencies to README
Merge branch 'other_fonts'

Conflicts:
	README.md
Merge branch 'python_deps'
use a requirements file to manage python deps