Support for rendering partials

Partials can now be rendered by calling render 'path/to/partial.erb' in the template.

Enable ERB trim mode and add examples

• Enabled trim mode for ERB templates using a hyphen (e.g. <%- code -%> will remove preceeding indentation and a following newline).
• Added Example directory giving real usage examples in terraform.

Initial release

Initial release, reads json from stdin, takes path to ERB template as first argument, outputs json object with rendered template as the value to key "rendered".