btc to usd conversion


**What does your Instant Answer do?**
	This is a spice that converts BTC to USD using current exchange rates at blockchain.info

**What problem does your Instant Answer solve (Why is it better than organic links)?**
	It is faster than going to a website and finding a conversion tool there.

**What is the data source for your Instant Answer? (Provide a link if possible)**
	http://blockchain.info/ticker

**Why did you choose this data source?**
	It is an authoritative source

**Are there any other alternative (better) data sources?**
	There are alternative sources that use different exchanges for their conversions

**What are some example queries that trigger this Instant Answer?**
	10 btc to usd
	0.5 btc to usd

**Which communities will this Instant Answer be especially useful for? (gamers, book lovers, etc)**
	bitcoin enthusiasts

**Is this Instant Answer connected to a DuckDuckHack [Instant Answer idea](https://duck.co/ideas)?**
	yes

**Which existing Instant Answers will this one supersede/overlap with?**
	DDG::Spice::Bitcoin.pm

**Are you having any problems? Do you need our help with anything?**
	None

**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?**
	None

**Where did you hear about DuckDuckHack? (For first time contributors)**
	Teh Intarwebz

## 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:
    - Mac OSX
        [x] Google Chrome
        [x] Firefox
        [] Opera
        [x] Safari

```