Update to org-ruby 0.9.1, explicitly disable including files feature 

Update the `org-ruby` gem to recent version and explicitly disable the `#+INCLUDE:` directive making it more suitable for when running in Github environment. Recent version also adds `lang` attributes to code blocks so that syntax highlight is supported (fixes #253 and #250)

```
# Disable including files!
Orgmode::Parser.new(content, :allow_include_files => false).to_html
```