Support go get for installation

[friism]

λ  go get github.com/docker/communitytools-image2docker-linux
# cd .; git clone https://github.com/docker/v2c c:\code\go\src\github.com\docker\v2c
Cloning into 'c:\code\go\src\github.com\docker\v2c'...
remote: Repository not found.
fatal: repository 'https://github.com/docker/v2c/' not found
package github.com/docker/v2c/api: exit status 128
package github.com/docker/v2c/system: cannot find package "github.com/docker/v2c/system" in any of:
        C:\Go\src\github.com\docker\v2c\system (from $GOROOT)
        c:\code\go\src\github.com\docker\v2c\system (from $GOPATH)
package github.com/docker/v2c/workflow: cannot find package "github.com/docker/v2c/workflow" in any of:
        C:\Go\src\github.com\docker\v2c\workflow (from $GOROOT)
        c:\code\go\src\github.com\docker\v2c\workflow (from $GOPATH)

[pdevine]

Let's track this w/ issue #15