Add ATTRIBUTION.md to About IITC pop up
Use already read file instead of rereading
Only need markdown and not GFM for .md files
More changes from gfm to md
Build script fixes to work on both python 2 and 3
Merge pull request #174 from Fragger/about-attribution

Add ATTRIBUTION.md to About IITC pop up
bugfix: http2https
updated internal poslink click handle (see #149)
fixed typo
Merge remote-tracking branch 'upstream/master' into gh-pages