Add support for building and bundling windows binaries.

[matthewhartstonge]

As a first step towards #116 I've added windows support to the makefile for creating binaries.

[matthewhartstonge]

currently there is one test failing under windows, I'll have a look into this.

=== RUN   TestGetListener
--- FAIL: TestGetListener (0.00s)
        Error Trace:    server_test.go:47
        Error:          Expected nil, but got: &errors.errorString{s:"failed to listen unix socket: listen unix /tmp/gaurun.sock: bind: A socket operation encountered a dead network."}

[matthewhartstonge]

Looks like the p12 certificate has expired under gaurun/buford/testdata/cert.p12

[cubicdaiya]

Since gaurun does not use p12 in actual, we removed the code to handle p12 in #146.