Increase the robustness of the chef module

Add the following adjustments to the chef template and module

- Make it so that the chef directories can be provided (defaults
  to the existing directories)
- Make the params much more configurable, and if a parameter is
  provided in the chef configuration it will override existing template
  parameters.
- Make the template skip lines if the values are None in the configuration
  so that template lines can be removed if/when this is desirable.
- Allow the firstboot json path to be configurable (defaults to the
  existing location).
- Adds a basic set of tests to ensure that good things are happening.

templates/chef_client.rb.tmpl

@@ -9,17 +9,51 @@ you need to add the following to config:
     validation_name: XYZ
     server_url: XYZ
 -#}
-log_level              :info
-log_location           "/var/log/chef/client.log"
-ssl_verify_mode        :verify_none
+
+{#
+The reason these are not in quotes is because they are ruby
+symbols that will be placed inside here, and not actual strings...
+#}
+# This is a generated file, created on {{generated_on}}.
+{% if log_level %}
+log_level              {{log_level}}
+{% endif %}
+{% if ssl_verify_mode %}
+ssl_verify_mode        {{ssl_verify_mode}}
+{% endif %}
+{% if log_location %}
+log_location           "{{log_location}}"
+{% endif %}
+{% if validation_name %}
 validation_client_name "{{validation_name}}"
-validation_key         "/etc/chef/validation.pem"
-client_key             "/etc/chef/client.pem"
+{% endif %}
+{% if validation_key %}
+validation_key         "{{validation_key}}"
+{% endif %}
+{% if client_key %}
+client_key             "{{client_key}}"
+{% endif %}
+{% if server_url %}
 chef_server_url        "{{server_url}}"
+{% endif %}
+{% if environment %}
 environment            "{{environment}}"
+{% endif %}
+{% if node_name %}
 node_name              "{{node_name}}"
-json_attribs           "/etc/chef/firstboot.json"
-file_cache_path        "/var/cache/chef"
-file_backup_path       "/var/backups/chef"
-pid_file               "/var/run/chef/client.pid"
+{% endif %}
+{% if json_attribs %}
+json_attribs           "{{json_attribs}}"
+{% endif %}
+{% if file_cache_path %}
+file_cache_path        "{{file_cache_path}}"
+{% endif %}
+{% if file_backup_path %}
+file_backup_path       "{{file_backup_path}}"
+{% endif %}
+{% if pid_file %}
+pid_file               "{{pid_file}}"
+{% endif %}
+{% if show_time %}
 Chef::Log::Formatter.show_time = true
+{% endif %}