import_examples script

Adds `import_examples` script to import latest examples from GitHub. This script is (reasonably) generic, and can be shared between Artoo and Gobot with minimal configuration changes.

To use the script simply run `./bin/import_examples` script, and it will:

- clone down the Artoo repo into `.artoo`
- find all Ruby examples in the cloned repo
- convert those to HAML example pages
- generate an index page
- remove the copy of the Artoo repo

:palm_tree: