Special case for .ttf files
Simplified, to catch all .ttf files
fix missing main/lib dir if py lib in requirements not found
remove unused listing of installed_dirs
only run pip if necessary

This commit adds and modifies a pip_guard lockfile to temp each time
install_py_libs() is called. The file is used in later runs to check
if our requirements.txt is newer. If so pip install is run if not
it's skipped. run.py -C removes the file.
style changes as requested
style update: len(line) < 80
rename guard file
Merge pull request #137 from joernhees/pip_only_when_necessary

Pip only when necessary
Better handling if the dir lib not found
Merge pull request #54 from mdxs/ttf_mimetype

Explicit mime type for .ttf font files
Removed comment
Bumped pre-release version
Doctor is showing capitalized messages
Single quoates
Updated to -dev version
Updated README to reflect additions