feat: auto-rebuilding modules & FS watching

- Rename start command to autoreload.

- Base autoreload for a given module on its services' implied deploy
tasks (or just build, if the module doesn't define any services).

- Add version property and associated calculation methods to build &
deploy tasks, and modified getKey to incorporate versions when
appropriate.

- In connection with this change, build & deploy tasks are
now created via an async "factory" method, to ensure that the version
property for those task types has been computed before their getKey
method can be called.

- Modified TaskGraph to support inheritance/redo: If a task with the
same baseKey already already exists in the graph and is in progress
when a new task is added, the new task is set to inherit from the
in-progress task (see task-graph.ts for details).

README.md

@@ -12,6 +12,7 @@ You need to set up the following on your local machine to use garden:
 * Node.js >= 8.x
 * Git
 * rsync
+* [Watchman](https://facebook.github.io/watchman/docs/install.html)
 * [Docker for Mac/Windows (edge version)](https://docs.docker.com/engine/installation/)
 
 We recommend using Homebrew on Mac for everything except Docker. 

bin/bootstrap-osx

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 
 # install/update homebrew dependencies
-BREW_DEPS="cmake git kubectl stern rsync ruby"
+BREW_DEPS="cmake git kubectl stern rsync ruby watchman"
 
 brew update
 brew install ${BREW_DEPS}