Add possibility to run the script simply by its name in Linux

* Add an interpretator
* Change file permissions to be executable by Owner
Add Windows platform to Gemfile
Fix default `level` in Console
Improve security if notifier name is wrong
Split script classes to separate files and modules

Also:
* Move MESSAGES constant to Notifiers module
Fix not to use global variables
Refactor Console

* Move all the code to Console module.
* Make a base abstract class and separate implementations for different
  systems. This fixes a wrong encoding in console on Linux.
* Make global `console` methods which is available in all files where
  console.rb is included by `require`.
Fix checking page content due to changed page DOM

Now <p> doesn't contain <span>s with id "text2" and "textDate" and
contains `<span>[title:]</span> [date]`