Add mruby-process2

[katzer]

A fork of mruby-process with feature complete support for linux/mac/windows platforms.
I add here as the PR shows to update.

As the default branch is windows, is there a explicit way to define that in the .mgem file?

[matz]

I don't know how to deal with branches. We have to ask @bovi.

[katzer]

@bovi As the default branch is windows, is there a explicit way to define that in the .mgem file other than my intuitive approach?

[katzer]

@matz @bovi The default branch is master now. So the PR can get merged.

[bovi]

thanks @katzer

[katzer]

Thanks @bovi, that was fast