improve: add express option for template engine

In init procedure, add code that setup express custom template
engine and an option variable named "custom engine" that permit to
setup a custom template engine.
example:
  engine = require('ejs-locals');
  keystone.init({
      ...
      'custom engine': engine,
      ...
      });
Merge pull request #92 from JeremyFouriaux/master

improve: add express option for template engine
More robust / consistent initialisation of options w/ process.env variables
Better implementation of cloudinary config, fixes #69
documentation: document custom template engine option

this add a sample of usage for using custom engine option that permit to
use a custom template engine not included by default.
Merge pull request #99 from JeremyFouriaux/master

Documentation: document custom template engine option
Fixing a typo in the getting started guide
Adding an API action for creating items, related to #102
Adding instructions for using a development version of Keystone with npm link
Updating keystone-utils
Adding cms keyword
Correctly escaping HTML entities in names through the API
v0.1.53
Updating Changelog
Fixing initialisation when cloudinary is not used
v0.1.54
Updating Changelog
Improving default option .env keys
Merry Christmas! and documentation :)
Fixing a typo in the getting started guide