ISO8601 stamp adjustments

Treat non-terminal templates correctly (2013-01-01T00:00:00-06:00 KK)

Correct vectorization bug

Remove ISO8601 format detection from inside stamp function.
add a comment in .strptime
cleanup and add more tests in test-stamp.R
cosmetic
add commented speed tests for stamp
comment "KK" stamp test, fails on Windows 7

  %z output format is completely screwed on Windows :(
Merge branch 'stamp-ISO8601' of git://github.com/vitoshka/lubridate into vitoshka-stamp-ISO8601