Tmux Cheat Sheet

**What does your instant answer do?**
Shows a cheat sheet for common Tmux commands.

**What problem does your instant answer solve (Why is it better than organic links)?**
Less data to sift through, faster access.

**What is the data source for your instant answer? (Provide a link if possible)**
http://www.openbsd.org/cgi-bin/man.cgi?query=tmux&sektion=1

**Why did you choose this data source?**
Because it's the man page.

**Are there any other alternative (better) data sources?**
No.

**What are some example queries that trigger this instant answer?**
tmux cheat sheet
tmux help
tmux reference

**Which communities will this instant answer be especially useful for? (gamers, book lovers, etc)**
Programmers/Sys-Admins

**Is this instant answer connected to a DuckDuckHack [instant answer idea](https://duck.co/ideas)?**
https://duck.co/ideas/idea/1197/tmux-cheatsheet

**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?**
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.
![screenshot](https://cloud.githubusercontent.com/assets/1291012/3500434/18f0c1d4-060b-11e4-9cb9-a45e87e982a8.png)


## 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://github.com/duckduckgo/duckduckgo-documentation/blob/master/duckduckhack/styleguides/design_styleguide.md)
[x] Tested cross-browser compatibility

    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
        [x] Google Chrome   
        [] Firefox         
        [] Opera           
        [x] Safari          

    - iOS (iPhone)
        [X] Safari Mobile   
        [X] Google Chrome   
        [] Opera           

    - iOS (iPad)
        [] Safari Mobile   
        [] Google Chrome   
        [] Opera            

    - Android
        [] Firefox         
        [] Native Browser  
        [] Google Chrome   
        [] Opera
```
@mintsoft I think you are right it probably doesn't matter and I don't feel strongly either way.  I think I could argue either side of this.

I did it out of habit.  Because in general its bad practice to have code run when you 'use DDG::Goodie::TmuxCheatSheet'.  When you 'use' a module you don't really expect the code to go off and access a file or a db or the internet or do anything at all.  I expect 'use' to just import a namespace.  So it violates the Principle of Least Astonishment.  Also running code during a 'use' can sometimes create a problem of circular dependencies.   Also it can slow down tests.  And it makes startup time slower.  

*However* I'm dubious any of those things really apply here.  

Btw cool idea for a cheatsheet @charles-l !