Pygments frenzy!

Now it's possible to choose any existing Pygments style that you want!
By the time I'm writing this these are all the available styles:
autumn, borland, bw, colorful, default, emacs, friendly, fruity, manni,
monokai, murphy, native, pastie, perldoc, rrt, solarizeddark,
solarizedlight, tango, trac, vim and vs. Also this commits removes the
statically coded background for highlighted code and lets the respective
pygment .css file take care of it. Also, by default, it will use
native.css style, the same used before this change.
rrt.css is too ugly and don't deserve to be commited
Keeps original bootstrap borders

Removed the borders tweaks in `.highlight pre` and `.linenodiv pre` and the custom `border-right`in `.linenodiv pre`.
Changes the way the pygments css are generated

Now the we're generated using ".highlight pre".
Added the pygments styles to README.md

Documented these changes in the README.md
Merge branch 'pygments-frenzy' of https://github.com/magnunleno/boothack into magnunleno-pygments-frenzy

* 'pygments-frenzy' of https://github.com/magnunleno/boothack:
  Added the pygments styles to README.md
  Changes the way the pygments css are generated
  Keeps original bootstrap borders
  rrt.css is too ugly and don't deserve to be commited
  Pygments frenzy!

Conflicts:
	README.md
	static/css/style.css