Installing on osx with homebrew libgroove fails

I tried installing libgroove using homebrew with

`brew install libgroove`

This installs fine, but when I tried to install waveform it kept complaining about the missing groove.h. It seems like node-gyp wants these libraries to be linked into /usr/X11 for some reason and they are not there by default after installing via brew. After running these commands

```
sudo ln -s /usr/local/Cellar/libgroove/4.3.0/lib/libgroove.dylib /usr/X11/lib/
sudo ln -s /usr/local/Cellar/libgroove/4.3.0/include/groove /usr/X11/include/
```

`npm install waveform` ran without a problem.

Maybe a mention in the readme for installing on osx via homebrew? or leave this issue in case someone else has this problem.

Thanks!