MKV support, parallel execution and colored output

Major release, several new features

• Multiple languages: now multiple languages can be downloaded at once.

• MKV support: creates mkv containers that include the original video plus all downloaded subtitles. Enable this by setting mkv=yes in the config file.
  (thanks to @nicodeceulaer for the suggestion!)

• New configuration: using standard ConfigParser for configuration; this will allow saner configuration options in the future.
  Previous users only have to edit their previous ~/ss.ini file and add a [ss] session:

  [ss]
  language=eng
  recursive=yes

• Parallel execution: now searches, downloads and embed mkv files in parallel (configured by parallel_jobs). This results in much better performance when downloading several subtitles at once.

• Colored output: using colorama;