Implicit type conversion error + String#start_with? and #end_with? error

[lumeet]

As of 2.0, MRI raises "no implicit conversion..." TypeError in certain situations. I've tried to make respective changes to TypeConverter. While not being sure it's 100% right, at least the following also seems to behave correctly with the patch.

$ rbenv shell 2.0.0-p598
$ ruby -e '"a" + 1'
no implicit conversion of Fixnum into String (TypeError)

$ rbenv shell jruby-9.0.0.0-dev
$ ruby -e '"a" + 1'
TypeError: can't convert Fixnum into String

The String part addresses then test_start_with?and test_end_with? in test_string.rb

[headius]

Thank you!