fix typo kodecocodes#249

Author: rayfix

README.markdown

@@ -68,7 +68,7 @@ Descriptive and consistent naming makes software easier to read and understand.
 - beginning factory methods with `make`
 - naming methods for their side effects
   - verb methods follow the -ed, -ing rule for the non-mutating version
-  - noun methods follow the formX rule for the non-mutating version
+  - noun methods follow the formX rule for the mutating version
   - boolean types should read like assertions
   - protocols that describe _what something is_ should read as nouns
   - protocols that describe _a capability_ should end in _-able_ or _-ible_