Version 2.0.0

Features:

• Support compile time template parsing.
• Added Crustache::parse_file_static to parse Mustache file on compile time.
• Added Crustache::loader to create FileSystem object to use Crustache::Engine.
• Added Crustache::loader_static, it is compile time version of Crustache::loader.

Changes:

• Add type annotation to class constructors for Crystal next compiler.