Fix `golint` complaints, use `filepath` instead of `path`, add color to README.

Hello!

I've made a few simple changes, mostly replacing usages of `path` for `filepath` for filesystem related path manipulation; since `path` is not portable across OS.  Also I've fixed the issues `golint` was reporting.  If you don't use `golint`, you can find it here: 

https://github.com/golang/lint
```bash
go get github.com/golang/lint/golint
```

Finally I've set the example code in the README to use Go syntax highlighting.