Remove the bang from our #stub! methods.

I'm not really sure why I used them when I wrote this in rspec-fire;
given there were not corresponding bang-less methods, it didn't
really make sense.

For rspec#144.

lib/rspec/mocks/example_methods.rb

@@ -42,7 +42,7 @@ def allow_message_expectations_on_nil
       end
 
       def stub_const(name, value, options = {})
-        ConstantStubber.stub!(name, value, options)
+        ConstantStubber.stub(name, value, options)
       end
 
     private

lib/rspec/mocks/stub_const.rb

@@ -26,7 +26,7 @@ def initialize(full_constant_name, stubbed_value, transfer_nested_constants)
           @transfer_nested_constants = transfer_nested_constants
         end
 
-        def stub!
+        def stub
           context_parts = @full_constant_name.split('::')
           @const_name = context_parts.pop
           @context = recursive_const_get(context_parts.join('::'))
@@ -96,7 +96,7 @@ def original_value
           # always nil
         end
 
-        def stub!
+        def stub
           context_parts = @full_constant_name.split('::')
           const_name = context_parts.pop
 
@@ -120,7 +120,7 @@ def rspec_reset
         end
       end
 
-      def self.stub!(constant_name, value, options = {})
+      def self.stub(constant_name, value, options = {})
         stubber = if recursive_const_defined?(constant_name)
           DefinedConstantReplacer.new(constant_name, value, options[:transfer_nested_constants])
         else
@@ -129,7 +129,7 @@ def self.stub!(constant_name, value, options = {})
 
         stubbers << stubber
 
-        stubber.stub!
+        stubber.stub
         ensure_registered_with_rspec_mocks
         stubber.original_value
       end