Made sure we include the module name for SchemaParseErrors

If you pass an unrecognized object for the schema, we should be raising a SchemaParseError, however instead right now a NameError is raised, beacuse we're not correctly qualifying the error class with it's module.

I've corrected the class/module name and added tests.

This fixes voxpupuli#292

lib/json-schema/validator.rb

@@ -569,7 +569,7 @@ def initialize_schema(schema)
         end
         Validator.add_schema(schema)
       else
-        raise SchemaParseError, "Invalid schema - must be either a string or a hash"
+        raise JSON::Schema::SchemaParseError, "Invalid schema - must be either a string or a hash"
       end
 
       schema

test/test_ruby_schema.rb

@@ -56,4 +56,10 @@ def test_symbol_keys_in_hash_within_array
 
     assert_valid schema, data, :validate_schema => true
   end
+
+  def test_schema_of_unrecognized_type
+    assert_raises JSON::Schema::SchemaParseError do
+      JSON::Validator.validate(Object.new, {})
+    end
+  end
 end