Implementing IO#pos/IO#tell, IO#pos=
Fixing translation and adding an extra test

which may well be overkill, but it helped me figure out the translation
problem.
Aliased method is aliased
Changes per feedback regarding IO#pos= definition and IO#pos retval truncation
Merge pull request #462 from modcloth/mbh/IO#pos

Implementing IO#pos/IO#tell, IO#pos=