Allow Jenkins Environment variables in Faux Project Path

[mklauber]

This plugin does not expand environment variables like ${WORKSPACE} when they are placed in the Faux Project Path. I'm attempting this because I'm using the capability the git plugin to checkout into a subdirectory of the workspace, and I run all my commands in that subdirectory. This plugin cannot find the source files when I do so, because the pep8 report doesn't reference that directory.