National independence day goodie

**What does your Instant Answer do?**
Answers what the independence day of a country is.

**What problem does your Instant Answer solve?**
It answers quite a specific question that has one right answer.

**What is the data source for your Instant Answer?**
Wikipedia, list of national independence days 
https://en.wikipedia.org/wiki/List_of_national_independence_days

**Why did you choose this data source?**
It was suggested on the ddg forums 
https://duck.co/ideas/idea/4546/national-independence-day

**Are there any other alternative (better) data sources?**
Perhaps?

**What are some example queries that trigger this Instant Answer?**
- *independence day, papua new guinea*
- *when is the independence day of norway?*

**Which communities will this Instant Answer be especially useful for?**
The general population

**Is this Instant Answer connected to a DuckDuckHack [Instant Answer idea](https://duck.co/ideas)?**
Yes, https://duck.co/ideas/idea/4546/national-independence-day


**Which existing Instant Answers will this one supercede/overlap with?**
None that I know of.

**Are you having any problems? Do you need our help with anything?**
Not any in particular. Is there a perferred way to store data in text file? I currently use JSON.

**Where did you hear about DuckDuckHack?**
Via the learn more button on the front page of duckduckgo.com, I think. 

**What does the Instant Answer look like?**
Returns a plain text string.

## Checklist
Please place an 'X' where appropriate.

```
[X] Added metadata and attribution information (https://duck.co/duckduckhack/metadata)
[X] Wrote test file and added to t/ directory (https://duck.co/duckduckhack/goodie_tests)
[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)
[] Tested cross-browser compatibility
    Developed with firefox on ubuntu, but I assume this doesn't apply since is a plaintext answer
    
```

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