Use `time.Since` instead of `time.Now.Sub`.
Use `http` codes.
Calm `golint` gods.

* Capitalization of acronyms.
* Remove useless `else { return }` clause.
* Arrange comments.
Handle error when closing files.

There are two other un-handled errors here :

```
$GOPATH/src/github.com/codegangsta/martini/router.go:234:13 res.Write([]byte(vals[1].String()))
$GOPATH/src/github.com/codegangsta/martini/router.go:236:13 res.Write([]byte(vals[0].String()))
```
I've ignored them for now.
Rename in `router_test` too.
Revert "Handle error when closing files."

This reverts commit 468b32397d98b0fff59dc965f77419c419676f7c.
Merge pull request #93 from aybabtme/24pullrequest

Use `http.Status...`, `time.Since`, calm `golint`, handle errors.