Create symlink for emacsclient in use! method.

I started to use evm in linux and the emacsclient binary is not present. The PR solves this. 

@rejeep, I'm not totally convinced with this approach, If you have a better idea I will be happy to modify this PR.
I'll add specs after receiving your feedback. Thanks!

ps: I'm not 100% sure, but emacsclient in mac osx is not working well, right?