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
```
I'm trying to encourage everyone to put the guard clauses before the "work" clauses, as much as possible.  This may allow us to "short circuit" earlier, doing less work and provides a natural place to do "more work" if we decide to do so later.

For this one it would be something like:

```perl
return unless (defined $country and defined $vaildDate);

return uc $countries{$country}, $vaildDate;
```

I'm pretty sure the `duckpan new` template uses the style you have here, so it's all on us that you're doing it that way.. :grin: