Clarify behavior of --example command line option

- Closes #378.
- Also see #299.

lib/rspec/core/option_parser.rb

@@ -40,8 +40,7 @@ def parser(options)
           options[:debug] = true
         end
 
-        parser.on('-e', '--example PATTERN', "Run examples whose full descriptions match this pattern",
-                "(PATTERN is compiled into a Ruby regular expression)") do |o|
+        parser.on('-e', '--example STRING', "Run examples whose full nested names include STRING") do |o|
           options[:full_description] = Regexp.compile(Regexp.escape(o))
         end