README improvement

This contains some additions to the README, specifically Debian/Ubuntu requirements.
Merge pull request #1 from bjoska/readme_update

prerequisites for Debian/Ubuntu
Rakefile: addition of a console task.

Run with:

```sh
$ rake console
```

You will now have a console started with the gem already loaded and
ready.
rearrange README usage chapter
Merge branch 'bjoska-rake_addition' Closes #4

Merge bjoska changes, with README rearrange.
BlinkStick::Version addition

This was commented earlier, but has now been corrected.
BlinkStick and ColorHandler

Extraction of methods relating to color change etc.

Rework of the code in BlinkStick in general. Removal of class variables
in favor of constants and a class instance variable.

Plus some general refactoring of methods.
Color, Parse and Hex corrections
Merge pull request #2 from bjoska/major_rework

Refactoring and more tests