support godep save -copy
godep go get is meaningless
advertise godep save -copy
read Go version from Godeps if present
test Godeps vendored path
update godep to 05aebf; fixes #30
include platform extension for future releases

The Go 1.2 series of release candidates have included
more than one darwin build, distinguished by a file
extension for the specific version of Mac OS X each
one runs on. Assume this extension will be present for
all future Go releases and assume version 10.8 works
for the user. (This change has no effect for Heroku
builds; it only affects testing on Darwin systems.)
update godep ad for new default behavior
revert to old buildpack and go build ./... before go get