0.66.0

• fixes uint64 casting (#250)
• fixes byte casting (#257)
• fixes a couple of places where bytes wasn't properly translated to byte[] (#252, #271)
• adds contract importing (#136)
• adds operator assignment (#179)
• fixes various problems with ufixed encoding and math
• adds OnCompletion enum
• removes templateVar function (replace with TempalteVar property)
• adds better key collision detection
• fixes method definition order bug (#267)
• fixes calling public methods (#268)
• Improvement in how TEALScript uses the frame for variables and return values