Add Rake task
Add Rake task

Allow `haml-lint` to be invoked via Rake task. Example usage:

    require 'haml_lint/rake_task'

    HamlLint::RakeTask.new(:amirite?) do |task|
      task.include_linter = %w[ImplicitDiv RuboCop]
      task.exclude_linter = %w[TagName]
      task.config = File.expand_path("~/.haml_lint.yml")
      task.exclude = %W[#{File.expand_path("some/path.haml")}]
      task.pattern = 'views/**/*.haml'
    end

    task default: :amirite?

Change-Id: I903b08308ef40a1dab6af5ba2c20eb09742240de
Reviewed-on: http://gerrit.causes.com/40774
Tested-by: jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@causes.com>
Reviewed-by: Shane da Silva <67fb7bfe39f841b16a1f86d3928acc568d12c716@brigade.com>

mzp/haml-lint,skateman/haml-lint