Add gopm support

[guilhem]

To help #90 I try to use gopm

For the moment I have a .gopmfile like this:

[target]
path = github.com/hashicorp/consul

[deps]
github.com/mitchellh/cli = 
github.com/hashicorp/logutils = 
github.com/ryanuber/columnize = 
github.com/armon/circbuf = 
github.com/armon/go-metrics = 
github.com/hashicorp/serf = 
github.com/miekg/dns = 
github.com/mitchellh/mapstructure = 
github.com/ugorji/go = 
github.com/armon/gomdb = 
github.com/hashicorp/memberlist = 
github.com/hashicorp/raft = 
github.com/hashicorp/raft-mdb = 
github.com/inconshreveable/muxado = 

[res]
include = 

but fail because of dir naming:

cannot create consul: Is a directory
gopm ERR! build fail to build program:
gopm ERR!   exit status 2

[mitchellh]

We'd like to improve the reproducible build situation but we haven't quite decided what tool we'd like to use yet. You're free to use gopm on your own.