Annual Rainfall Instant Answer

Here goes nothing! Please by nice this is my first contribution :blush:
Looking forward to making any changes necessary :+1:  

**What does your Instant Answer do?**
Returns the average annual rainfall (precipitation) in millimeters for a searched country.  

**What problem does your Instant Answer solve (Why is it better than organic links)?**
It provides people searching for specific annual rainfall a quicker option then viewing a Wikipedia article or browsing another site.

**What is the data source for your Instant Answer? (Provide a link if possible)**
[WorldBank.org](http://data.worldbank.org/indicator/AG.LND.PRCP.MM) indicator API data.

**Why did you choose this data source?**
Reliable and accurate data source. Free! 

**Are there any other alternative (better) data sources?**
No. Not that provide average precipitation data.

**What are some example queries that trigger this Instant Answer?**
rainfall Australia

**Which communities will this Instant Answer be especially useful for? (gamers, book lovers, etc)**
Anyway interested in Weather Data!

**Is this Instant Answer connected to a DuckDuckHack [Instant Answer idea](https://duck.co/ideas)?**
Yes! https://duck.co/ideas/idea/4502/annual-rainfall

**Which existing Instant Answers will this one supersede/overlap with?**
None.

**Are you having any problems? Do you need our help with anything?**
The parts I'd like feedback/brainstorming on are a list of acceptable **triggers** and the **content template**. 

**What are the terms of use for the API? Will DuckDuckGo need specific authorization (e.g. an API key)? Are there any costs associated with API usage?**
No API key required.
http://data.worldbank.org/summary-terms-of-use 
*You must include attribution for the data you use in the manner indicated in the metadata included with the data.*

**What does the Instant Answer look like? (Provide a screenshot for new or updated Instant Answers)**
![ejawcf3](https://cloud.githubusercontent.com/assets/5282264/4457221/64eaf084-4894-11e4-98b7-0119458fa848.png)

**Please help with the layout! It's ugly!**

## 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://duck.co/duckduckhack/design_styleguide)
[X] Verified that instant answer adheres to code styleguide (https://duck.co/duckduckhack/code_styleguide)
[X] Tested cross-browser compatibility

    Please let us know which browsers/devices you've tested on:
    - Windows 8
        [X] Google Chrome
        [X] Firefox
        [] Opera
        [] IE 10

    - Windows 7
        [X] Google Chrome
        [X] Firefox
        [] Opera
        [] IE 8
        [] IE 9
        [] IE 10

    - Windows XP
        [] IE 7
        [] IE 8

    - Mac OSX
        [] Google Chrome
        [] Firefox
        [] Opera
        [] Safari

    - iOS (iPhone)
        [] Safari Mobile
        [] Google Chrome
        [] Opera

    - iOS (iPad)
        [] Safari Mobile
        [] Google Chrome
        [] Opera

    - Android
        [X] Firefox
        [X] Native Browser
        [X] Google Chrome
        [X] Opera
```
@moollaza I mentioned before regarding the API returning null for the precipitation value if no data is available for that country. Assumed this check was enough? 

My concern was the fact it still makes an API call but unfortunately without a pre-built list of countries that we can use to check before we need to make the API call.