Add a small "contributing" file, for GitHub.
Add a small "contributing" file, for GitHub.

ssarangi/numba,gdementen/numba,pombredanne/numba,stuartarchibald/numba,stefanseefeld/numba,stuartarchibald/numba,jriehl/numba,IntelLabs/numba,pombredanne/numba,gdementen/numba,ssarangi/numba,gdementen/numba,stonebig/numba,stonebig/numba,stonebig/numba,sklam/numba,IntelLabs/numba,jriehl/numba,pitrou/numba,GaZ3ll3/numba,GaZ3ll3/numba,gmarkall/numba,gmarkall/numba,pitrou/numba,sklam/numba,GaZ3ll3/numba,cpcloud/numba,numba/numba,jriehl/numba,pombredanne/numba,pombredanne/numba,numba/numba,gdementen/numba,stonebig/numba,seibert/numba,IntelLabs/numba,ssarangi/numba,numba/numba,cpcloud/numba,seibert/numba,cpcloud/numba,gmarkall/numba,gmarkall/numba,seibert/numba,ssarangi/numba,GaZ3ll3/numba,gmarkall/numba,sklam/numba,jriehl/numba,numba/numba,GaZ3ll3/numba,IntelLabs/numba,stuartarchibald/numba,gdementen/numba,stonebig/numba,cpcloud/numba,pitrou/numba,stuartarchibald/numba,stefanseefeld/numba,stefanseefeld/numba,stefanseefeld/numba,pombredanne/numba,seibert/numba,numba/numba,IntelLabs/numba,cpcloud/numba,stuartarchibald/numba,stefanseefeld/numba,pitrou/numba,sklam/numba,sklam/numba,jriehl/numba,ssarangi/numba,pitrou/numba,seibert/numba