Limit deprecation output for non-generated messages

Conflicts:
	spec/rspec/core/formatters/deprecation_formatter_spec.rb
Eliminate DeprecationMessage mixin module

Conflicts:
	lib/rspec/core/formatters/deprecation_formatter.rb
Add period to end of message
Remove DeprecationWarning base class
Merge pull request #1125 from rspec/deprecation-formatter-2-99-cherrypicks

Deprecation formatter 2 99 cherrypicks