Add Configuration with templates

Part of the default behavior of this project will change when it is
released as a gem, since we no longer wish to install *all* of the hooks
in here by default.

I create a 'default' template, which ignores a subset of checks that are
Causes/gerrit-specific.

Not used yet, but soon...

Change-Id: I807601c2b8a83477ad72eeff198ae218c780d4fb
Reviewed-on: https://gerrit.causes.com/22692
Tested-by: Aiden Scandella <aiden@causes.com>
Reviewed-by: Joe Lencioni <joe.lencioni@causes.com>

Author: Aiden Scandella

config/templates.yml

@@ -0,0 +1,8 @@
+default:
+  excludes:
+    pre_commit:
+      - causes_email
+      - test_history
+      - restricted_paths
+    commit_msg:
+      - change_id

lib/overcommit.rb

@@ -1,3 +1,4 @@
+require 'overcommit/configuration'
 require 'overcommit/console_methods'
 require 'overcommit/git_hook'
 require 'overcommit/hook_specific_check'

lib/overcommit/configuration.rb

@@ -0,0 +1,19 @@
+require 'singleton'
+require 'yaml'
+
+module Overcommit
+  class Configuration
+    include Singleton
+
+    attr_reader :templates
+
+    def initialize
+      @templates = YAML::load_file(File.join(File.dirname(
+        File.expand_path(__FILE__)), '..', '..', 'config', 'templates.yml'))
+    end
+  end
+
+  def self.config
+    Configuration.instance
+  end
+end