Fetch file from systempath when loading "/environments" route
Fetch file from systempath when loading "/environments" route

* wqflask/wqflask/markdown_routes.py:
(render_markdown): Extend function to check whether "file_name" is to
be fetched remotely or locally in syspath.
(environments): Extend route to fetch from syspath if dependency file
exists there; otherwise fetch remotely from Github as a fallback.

genenetwork/genenetwork2,pjotrp/genenetwork2,zsloan/genenetwork2,pjotrp/genenetwork2,zsloan/genenetwork2,genenetwork/genenetwork2,pjotrp/genenetwork2,genenetwork/genenetwork2,genenetwork/genenetwork2,pjotrp/genenetwork2,pjotrp/genenetwork2,zsloan/genenetwork2,zsloan/genenetwork2