Add Redcarpet parsing and some colorings

Fixes #11 #15. To be merged with #14. Not fully working since switching to Markdown files.

- [x] Add possibility to colorize text (using Markdown image syntax)
- [ ] Syntax colorization (using Coderay or any other gem)
- [x] Parsing links (underscore and remove Md syntax)
- [x] ~~Tables~~ (to be implemented in future)
- [ ] Possibility to disable colors (i.e. for pipes)