updated readme
added another helper method
made setting cell values easier from table by using the string reference, e.g. "A1"
MS excel crashed with the popping of sheets, now using the :strong_hidden setting.
fixed test for raw reading
very basic xlsx writing (but note that date writing is not supported, unhappy with the current direction (basing on RubyXL))
simple performance test...
version update
removed performance test, not working as expected on ruby 1.9 and 2.0