Support for Login with session

[sathish316]

Support for crawling authenticated content.

Use Mechanize instead of Nokogiri to login and retain session info before crawling content that requires authentication

Example:

class Project
  html "http://jira.myproject.com"
  login "http://jira.myproject.com/login" do
    username {css: "form#login #username"}, value: "foo"
    password {css: "form#login #password"}, value: "bar"
    submit {css: "form#login #submit"}
  end
end