Fixed TwigTemplateEngine

• added missing return statement

TemplateEngine

• created TwigTemplateEngine
• created TemplateEngine
• renamed PrettyPrinterStrategy to CodeGenerator

BC breaks:

• PrettyPrinter's constructor now takes a TemplateEngine.

Locate

• Created Locate to simplify template localization

Import

• imported pretty printer from memio/memio v1.0.0-rc10