add method_missing to HTTParty class

Tests are valid if you merge previous pr(rspec syntax error fix) https://github.com/jnunemaker/httparty/pull/360

So, what i do?
1) 
```ruby
  def self.get(*args, &block)
    Basement.get(*args, &block)
  end

  def self.post(*args, &block)
    Basement.post(*args, &block)
  end

  def self.patch(*args, &block)
    Basement.patch(*args, &block)
  end

  def self.put(*args, &block)
    Basement.put(*args, &block)
  end

  def self.delete(*args, &block)
    Basement.delete(*args, &block)
  end

  def self.move(*args, &block)
    Basement.move(*args, &block)
  end

  def self.copy(*args, &block)
    Basement.copy(*args, &block)
  end

  def self.head(*args, &block)
    Basement.head(*args, &block)
  end

  def self.options(*args, &block)
    Basement.options(*args, &block)
  end
```
This code in [lib/httparty.rb](https://github.com/jnunemaker/httparty/blob/master/lib/httparty.rb#L562) looks repeatable, i think it will be nice to have more light dynamic behaviour:
```ruby
class << self   
   def method_missing(name, *args, &block)
      if Basement.respond_to?(name)
        Basement.send(name, *args, &block)
      else
        super
      end
    end
end
```
2) There are two methods in HTTParty class: ```self.normalize_base_uri``` and ```self.included```, so i moved it without self to ```class << self``` above
3) 
```ruby
  class Basement #:nodoc:
    include HTTParty
  end
```
Move this after ```class << self``` ( because ```def included``` above must be declared before it is really included in Basement)

Tests for this pr is not needed, because this basic behavior like ```HTTParty.get(url)``` has already tested in a lot of rspec/cucumber tests.