Use strptime with format '%m/%d/%Y' if all else fails on date parsing.
Adjusted tests for string_optimistic_date_converter so that expected result reflects change in
Date.parse for two year dates between Ruby 1.8.7 and Ruby 1.9
Updated docs
Merge branch 'strptime_date_parsing' of github.com:benefitter/workbook into benefitter-strptime_date_parsing
removed the test for 12/23/80 as the expected should probably have been 12/23/1980 (instead of 12/23/0080)