Merge pull request #57 from artas360/master

Adding file support based on C FILEs.
Bug correction : enumerate and xrange
* Enumerate : enumerating over an generator expression and used inside another operator like map
* xrange : max(xrange(...))
* test cases
Merge pull request #58 from Nagadum/bugfix

Bug correction : enumerate and xrange
Bug correction : file iterator and adding string implicit conversion