Install to project instead of $HOME

[s0kil]

Currently, Node.JS is installed to ~/.crystal-nodejs, it would be better if it was installed on the same path as the project using the crystal-nodejs library.

[fukaoi]

@s0kil thanks your issue.

When crystay build, and bin/* single binary if developer copied to /usr/local/bin/* that lib/nodejs/crystal-nodejs is need copy. It is troublesome.

To solve it, I thought that I could specify the environment variable and specify the crystal-nodejs directory.

e.g

CRYSTAL_NODEJS_LIB=/usr/local/lib/crystal-nodejs /usr/local/bin/Demo

I think about this.