added boolean and null comparisson support
readme version update
!IMPORTANT : Removed the extra two optional parameters for the method 'a' / 'an'

Removed the ternary operator in which the method 'a' & 'an' returned
values instead just true or false.

so only this kind of comparison is possible:

is ( something ).an( Array );
readme update
gitignore addition.
Option to add a different container.