Excel: shows description of an Excel function

**What does your instant answer do?**
It shows the description of an Excel function.

**What problem does your instant answer solve (Why is it better than organic links)?**
Same as above.

**What is the data source for your instant answer? (Provide a link if possible)**
Office ([http://office.microsoft.com/](http://office.microsoft.com/en-001/excel-help/excel-functions-alphabetical-HA102753227.aspx)).

**Why did you choose this data source?**
Official.

**Are there any other alternative (better) data sources?**
None.

**What are some example queries that trigger this instant answer?**
```excel sum```, ```sum excel```

**Which communities will this instant answer be especially useful for? (gamers, book lovers, etc)**
People who wanted to know what a specific Excel function do.

**Is this instant answer connected to a DuckDuckHack [instant answer idea](https://duck.co/ideas)?**
Nope.

**Which existing instant answers will this one supersede/overlap with?**
None.

**Are you having any problems? Do you need our help with anything?**
Nope.

**\*\*Note:** Please attach a screenshot for new instant answer pull requests, and for pull requests which modify the look/design of existing instant answers.
![excel](https://cloud.githubusercontent.com/assets/7313210/2739412/09dbb480-c6ad-11e3-9296-6d87c3cfde48.png)

```
[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://github.com/duckduckgo/duckduckgo-documentation/blob/master/duckduckhack/styleguides/design_styleguide.md)
[] Tested cross-browser compatability

    Please let us know which browsers/devices you've tested on:
    - Windows 8
        [] Google Chrome   
        [] Firefox         
        [] Opera           
        [] IE 10           

    - Windows 7
        [] Google Chrome   
        [] 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
        [] Firefox         
        [] Native Browser  
        [] Google Chrome   
        [] Opera

    - Linux
        [X] Firefox
```