Add an "engines" property to warn node 0.11/0.12 users

[hristozov]

As we know (#15), this package won’t work on node 0.11 and 0.12.

This small pull request adds an appropriate engines property in package.json to warn people which attempt to install it on these versions of node, saving them some googling after a build failure.

For example, on my machine this produces something like:

$ npm install ~/src/node-fann
npm WARN engine fann@0.2.4: wanted: {"node":"<0.11"} (current: {"node":"0.12.2","npm":"2.7.5"})

> fann@0.2.4 install /Users/gh/tmp/node_modules/fann
> node-gyp rebuild

…

This restriction should be removed once the 0.11 support is ready.

[rlidwka]

I added support for node versions 0.12.x, 1.x and 2.x in 31a251d. Thanks for the reminder. :)

[hristozov]

Thank you very much! :)