synchronizeFile() should not be run implicitly after .write(s).
stdin handler should be opened for writing and not reading.
Optimized str1.`in`(str2). Added note about str1.find(str2) slowness.
Added tests for "str1 in str2" (Python) + "str1.`in`(str2)" (Swift).
Merge branch 'master' of github-as-practicalswift:practicalswift/Pythonic.swift