Escape grep_for text when using grep

The rak code already does this and it is necessary for grep as well.

lib/application_checker.rb

@@ -201,7 +201,7 @@ module Rails
       def find_with_grep(text, where)
         value = ""
       
-        Open3.popen3("grep -r '#{text}' #{where}") do |stdin, stdout, stderr|
+        Open3.popen3("grep -r '#{Regexp.escape(text)}' #{where}") do |stdin, stdout, stderr|
           value = stdout.read
         end