Async Support (#17)

* Set up nix dev environment

* Async under the src directory

* Async in build script

* Async shouldn't be default

* Forgot Stream waiting

* Actually tagging the one I forgot with async

* Added some forgotten Asyncs

* Debug Logging

* some more logging

* Another forgotten await

* Proper decoding of messages, including waiting for the whole message

* Rename feature to make it clear it's specific to the tokio rt

* Remove debug logging

* Replace condvar with notify

* Fix some clippy lints

* Document the new option

.envrc

@@ -0,0 +1 @@
+use flake

.gitignore

@@ -2,3 +2,6 @@
 /krpc_codegen/target
 # service_definitions/
 .idea
+
+# Direnv
+.direnv