Release Notes 2018.06.20

* Turtle Islands
* Turtle Sails (exclusively found on turtle islands)
* Option to return to build mode from place boat mode
* Fixed error which could cause boat name menu to appear at wrong times
* Clarified the below-minimum-specification warning menu
* Fixed issue which caused player to slide off some rotating pieces
* Improved sail behaviors when sideways, upside down, or propped open