Buildout recipe to install phantomjs/casperjs

The recipe supports the following options:

phantomjs-url

Url to download phantomjs

phantomjs-version

Try to retreive phantomjs url from version

casperjs-url

Url to download casperjs

We'll start by creating a buildout that uses the recipe:

>>> write('buildout.cfg',
... """
... [buildout]
... parts = casperjs
...
... [casperjs]
... recipe = gp.recipe.phantomjs
... """)

>>> system('buildout')

>>> ls('bin')
-  buildout
-  casperjs
-  phantomjs