Questions containing fractions should return fraction result

# Goodie Pull Request Template

Using this template will help us better understand your Instant Answer and assist you when necessary.  Simply copy and paste the markdown below into the description of your GitHub pull request and complete as appropriate.

**What does your Instant Answer do?**
Returns a fraction math result if the query contains fractions

**What problem does your Instant Answer solve (Why is it better than organic links)?**
Currently the calculator only returns decimal answers, this feature adds the answer in fraction form

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N/A

**Why did you choose this data source?**
N/A

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N/A

**What are some example queries that trigger this Instant Answer?**
"3/7 + 5/6", "1/4 + 2/4";

**Which communities will this Instant Answer be especially useful for? (gamers, book lovers, etc)**
Anyone who has the need for a calculator

**Is this Instant Answer connected to a DuckDuckHack [Instant Answer idea](https://duck.co/ideas)?**
Yes

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## Checklist
Please place an 'X' where appropriate.

```
[] 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)
    Appended tests to the existing Calculator.t
[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
        [] Google Chrome
        [] Firefox
        [] Opera
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    - Windows 7
        [X] Google Chrome
        [X] Firefox
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        [] IE 8
        [] IE 9
        [X] IE 10

    - Windows XP
        [] IE 7
        [] IE 8

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```

I agree and "up-conversion" will not happen, the fraction format is there as a supplement to the decimal answer, so users will never only receive the fraction format.  Also the fraction should only show if the input expression contains any division operations.