Add Contributing guideline#555

Merged

nicolaiskogheim merged 3 commits intotj:masterfrom

spacewander:contributing

Jul 31, 2016

Commits on Jul 27, 2016

Add contributing guideline
spacewander
committed

Commits on Jul 29, 2016

modify CONTRIBUTING.md
spacewander
committed

Commits on Jul 30, 2016

modify CONTRIBUTING.md again
spacewander
authored