Add a JSON handler to serve dynamic data

[datenimperator]

To test dynamic components serve needs to properly handle responses in json format. The patch adds a file handler that will serve files with extension .json as such, and parse YAML files .yml to send the results as json, too.

[jlong]

Did I reply on this? I'm on board with this, just not sure about delivering YAML as JSON. Can we back out of that?

[jlong]

Also, we should update the "test_project" with a few test files.

[datenimperator]

Hm, my email reply didn't get to here? I wasn't sure about YAML, either. However, YAML mixins allow to build bigger data structures more easily, so I figured it might be a good idea.

---
base: &base
  occupation: 'Thief'
  weapon: 'Revolver'
data:
- firstname: 'Joe'
  lastname: 'Dalton'
  <<: *base
- firstname: 'Averell'
  lastname: 'Dalton'
  <<: *base

which gives us a data structure of

{
  "base": {
    "weapon": "Revolver", 
    "occupation": "Thief"
  }, 
  "data": [
    {
      "firstname": "Joe", 
      "lastname": "Dalton", 
      "weapon": "Revolver", 
      "occupation": "Thief"
    }, 
    {
      "firstname": "Averell", 
      "lastname": "Dalton", 
      "weapon": "Revolver", 
      "occupation": "Thief"
    }
  ]
}

[jlong]

Yeah, I can see the advantage.

Perhaps the extensions for YAML/JSON parsing should be .json.yml and .json.yaml. I don't want to override regular YAML files just for this.

If you will rebase on jlong/master, add some test files to test_project, and fix the extension issue for YAML, I'll merge.