Modified Gesv to accept nil pivots and complex matrices

[jvlmdr]

Hey, a few minor modifications:

I've let Gesv() accept a nil argument for ipiv according to the spec.
Gesv() will also now call zgesv() if the arguments are complex.
I didn't add this for other functions e.g. Gels().
The symbols cdotusub and zdotusub weren't found on OS X.
Added linux/darwin switches for cgo.
Removed dependency on atlas.
Ran gofmt.

Let me know if you'd like only a subset of these.

[hrautila]

At the moment I could do without the gofmt part. It looks like it changes all the lines. Personally I have used indentation of 4 with spaces.

[jvlmdr]

(Thanks for the work you've done on this library!)

I can understand not wanting to have a singularity in your commit history where everything changed but nothing changed. This is the problem that gofmt is supposed to solve though!

[hrautila]

Unfortunately gofmt can be invoked with parameters :) I used following when I originally run gofmt to the libbary: gofmt -w -tabs=false -tabwidth=4 $*