Overloard imports runtime on godocs

[Julian-Mentasti]

Some libraries use the Godoc documentation library where they have a doc.go file where they only declare the package name and have a comment block with documentation.

When you run overload in instrument mode and you "instr" block in your json config has the following:

    "instr" : {
        "dir" : "/home/julian/go/src/github.com/gorilla/websocket/",
        "blocks_file" : "../examples/websocket/blocks"
    },

It will instrument all .go files meaning it will also try to instrument the documentation files. This means that its importing runtime but never using it in some files thus the go compiler will prevent it from being compiled due to the unused library.