Lazy iteration over NSFileHandle.

It still reads entire _files_ at once (availableData does that), but the actual splitting up into lines happen only as needed.
Streams are read in chunks if possible (availableData does that too).
Merge branch 'master' of https://github.com/practicalswift/Pythonic.swift

# By practicalswift
# Via practicalswift
* 'master' of https://github.com/practicalswift/Pythonic.swift:
  Fixed typo.
  Now using shorthand notation [A] and [A:B] exclusively for arrays and dictionaries.
  239x speed-up achieved by working around known Dictionary bug.
  Remove redundant var typo.
  Added note about Python compatibility set(…).
  The Python compability set(…) is now a function instead of a subclass.
  Allow for setting sys.argv
Merge pull request #7 from kareman/master

Lazy iteration over NSFileHandle