pgte/nock — pull request #199 by lakenen (2014-06-16 20:42:44+00:00)
Title: Allow matching header with a function

e.g.:

```js
var scope = nock('http://api.myservice.com')
.matchHeader('content-length', function (val) {
return val >= 1000;
})
.get('/')
.reply(200, {
data: 'hello world'
})
```