Added NJT: New Jersey Transit train finder

**What does your instant answer do?**
Finds the next New Jersey Transit train from one station to another.

**What problem does your instant answer solve (Why is it better than organic links)?**
It lets travellers search for a train instead of using a timetable.

**What is the data source for your instant answer? (Provide a link if possible)**
I was playing with transit data this weekend and made [an endpoint](http://njt-api.appspot.com/) myself. It is hosted for free on Google App Engine. It should stay within the free quotas unless it gets really bogged down, but response time seems fast enough. It exposes data sourced from a General Transit Feed Specification (GTFS) feed [downloadable from the NJT website](https://www.njtransit.com/mt/mt_servlet.srv?hdnPageAction=MTDevLoginTo).

**Why did you choose this data source?**
The GTFS feed is the official source providing lines, stops, and schedules.

**Are there any other alternative (better) data sources?**
Not that I could find.

**What are some example queries that trigger this instant answer?**
`next train from metropark to new york`, `njt from atlantic city to philadelphia`

**Which communities will this instant answer be especially useful for? (gamers, book lovers, etc)**
Commuters that use NJ Transit

**Is this instant answer connected to a DuckDuckHack [instant answer idea](https://duck.co/ideas)?**
No, but this is kind of a "warm up" to doing an [MTA subway IA](https://duck.co/ideas/idea/913/nyc-subway-info)

**Which existing instant answers will this one supersede/overlap with?**
None

**Are you having any problems? Do you need our help with anything?**
Maybe design suggestions? Though I think it looks good as it is. ~~Unfortunately, NJT doesn't really provide real-time data, only an [XML Feed](https://www.njtransit.com/rss/RailAdvisories_feed.xml) that isn't standard.~~ NJT has [DepartureVision](http://m.njtransit.com/mo/mo_servlet.srv?hdnPageAction=DvTo) that appears to be scrapeable, I'll see what I can do in my API.

![screenshot from 2014-06-15 14 25 12](https://cloud.githubusercontent.com/assets/4411471/3281629/70c0959a-f4ba-11e3-9603-176949e75ce8.png)


## Checklist
Please place an 'X' where appropriate.

```
[x] Added metadata and attribution information
[x] Wrote test file and added to t/ directory
[x] Verified that instant answer adheres to design guidelines(https://github.com/duckduckgo/duckduckgo-documentation/blob/master/duckduckhack/styleguides/design_styleguide.md)
[/] Tested cross-browser compatability

    Please let us know which browsers/devices you've tested on:
    - Windows 8
        [] Google Chrome   
        [] Firefox         
        [] Opera           
        [] IE 10           

    - Windows 7
        [] Google Chrome   
        [] Firefox         
        [] Opera           
        [] IE 8            
        [] IE 9            
        [] IE 10           

    - Windows XP
        [] IE 7            
        [] IE 8            

    - Mac OSX
        [] Google Chrome   
        [] Firefox         
        [] Opera           
        [] Safari          

    - iOS (iPhone)
        [x] Safari Mobile   
        [x] Google Chrome   
        [] Opera           

    - iOS (iPad)
        [x] Safari Mobile   
        [x] Google Chrome   
        [] Opera            

    - Android
        [] Firefox         
        [] Native Browser  
        [] Google Chrome   
        [] Opera

    - Linux (Ubuntu)
        [x] Firefox
```

You control the API so `api_result` is probably always true, but sometimes DDG calls callback functions such as  `ddg_spice_njt` without any parameters in them if we encounter an error page https://github.com/duckduckgo/duckduckgo/blob/master/lib/DDG/Rewrite.pm#L173. So it's best to check for `api_result` for now.