Merge remote-tracking branch 'upstream/master' into Range
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Implement String#upto
Fix String#succ to properly handle carry
String#upto: fix 2 more special cases for single letters
String#upto: remove extra whitespace

Sorry. Old habits die hard...
raise NotImplmentedError instead of failing on unavailable Enumerator.new
Merge pull request #493 from obolzer/String#upto

Implement String#upto and fix String#succ