Run

`Editor` will now fully comply with the Open/Closed Principle via the `run` method.

* [x] [Create Editor::run #52](https://github.com/gnugat/redaktilo/issues/52)
* [x] [Create LineJumpAboveCommand / LineJumpBelowCommand #53](https://github.com/gnugat/redaktilo/issues/53)
* [x] [Create LineJumpPercentageCommand #54](https://github.com/gnugat/redaktilo/issues/54)
* [x] [Create LinePrependCommand and LineAppendCommand #55](https://github.com/gnugat/redaktilo/issues/55)
*  [x] Add those commands in the builder
* [x] Create a documentation listing the commands, their name, arguments...

![Run](http://www.impawards.com/2000/posters/chicken_run_ver1_xlg.jpg)
Why is `TextFactory` not cached like others instances?