    (-5).sign()
 => -1
 
-   (0).sign()
+   0.sign()
 => 0
 
-   (5).sign()
+   5.sign()
 => 1
 </pre></code>
 ###


@type Boolean
@returns true if this number is an even integer, false otherwise.
###
Number::even = ->
  this % 2 == 0


@type Boolean
@returns true if this number is an odd integer, false otherwise.

<code><pre>
   2.odd()
=> false

   3.odd()
=> true

   0.odd()
=> false     
</pre></code>
###
Number::odd = ->
  if this > 0
