Fully brainfuck compliant interpreter

Fixed misbehaving '[]':
* The opening brace is supposed to check if current value is null or not.
* The jump is supposed to happen over _matching_ braces, not just the next/previous one.
Comment support
Tests suite: added Hello World!
Disabled buffering and print comment char in usage output
Debug mode for Makefile
Merge pull request #1 from Ambrevar/master

Fully brainfuck-compliant interpreter