Concurrency support

• Added Future type support
• Added actors

Add ``Try`` type

v0.3.7

Fix version

Exceptions to Either translation helpers

v0.3.6

Fix tryST, tryET

First release

Added types: List, Option, Either, Stream. Function type is not usable due to nim-lang/Nim#3386

This release is already used in some projects, so it' s stable enough