Report only wrong predicate names

spec/ameba/rule/predicate_name_spec.cr

@@ -13,6 +13,9 @@ module Ameba::Rule
           def picture?(x)
           end
         end
+
+        def allow_this_picture?
+        end
       )
       subject.catch(s).should be_valid
     end

src/ameba/rule/predicate_name.cr

@@ -39,7 +39,7 @@ module Ameba::Rule
     end
 
     def test(source, node : Crystal::Def)
-      if node.name =~ /(is|has)_(\w+)\?/
+      if node.name =~ /^(is|has)_(\w+)\?/
         source.error self, node.location,
           "Favour method name '#{$2}?' over '#{node.name}'"
       end