go: go fmt github.com/chamaken/cgolmnfct/...

Thanks to shurcooL, I was able to grasp I should gofmt.
And update env refering http://blog.golang.org/go-fmt-your-code
expect: fix typo
conntrack: follow the original

conntrack: api: add two new bitmask functions
examples: update

fix import path and... I've forgotten constructor's signature.
and add note in nfct-daemon.go:
    This example requires CTA_MARK_MASK, introduced since 3.4
doc: update