YAML config file

[veelenga]

This PR prepares the following additions:

• Ameba runner
• YAML config loader
• Macro for Rule configuration properties
• YAML documented properties
• Sample configuration file
• CLI args

So now it is possible to define rule properties using prop macro:

struct SuperRule < Base
  prop max_length = 80
  prop enabled? = true
  prop wildcard = "*"

  def test(source)
    pp max_length, enabled?, wildcard
  end
end

which will automatically be mapped to MaxLength configuration property in YAML configuration file:

SuperRule:
  Enabled: false
  MaxLength: 100
  Wildcard: ".*" 

Closes #8