Update changelog and adopt version numbering

ChangeLog.md

@@ -1,19 +1,17 @@
 # Revision history for reflex-platform
 
-## 2a34ca864a5b51bf0f9f6cf94faf8996db7d6a5c - 2019-04-02
+This project's release branch is `master`. This log is written from the perspective of the release branch: when changes hit `master`, they are considered released, and the date should reflect that release.
+
+## v0.1.0.0 - 2019-04-03
 
 * Move git "thunks" to `dep/` dirs within each overlay, rather than one big
   `dep/` directory at the top level. This does make checking out thunks a bit
   more involved, but has the benefit of untangling reflex-platform a bit and
   making it more modular.
-
 * Many of the overlays have a `_dep` attribute with all the source derivations
   introduced by the overlay. This is just so `release.nix` can build all the
   sources, ensuring that these build-time dependencies also make it to the
   cache. This attribute is *not* intended to be overridden by consumers of
   reflex-platform. In particular it's possible the way we now push to the cache
   doesn't need this, and it will be removed entirely.
-
-## daabd633155da624198ed3302551bb2e834d2ac0 - 2019-03-29
-
 * Remove support for GHCs older than 8.4.