Add makefile for building

This add's a makefile that automates:
- Getting/Installing go
- Setting up paths
- Installing dependencies, godep, etc.
- Building the binary

Review: @jrconlin r?
It's suggested that you run build through godep (see https://github.com/tools/godep)
Might want to add 
```GODEPCMD = GOROOT=$(GOROOT) GOPATH=$(GOPATH) $(GODEP)```