Merge branch 'horizon-spec-0.3.0'

ChangeLog.md

 # Changelog for horizon-gen-nix
 
+## v0.3.0
+
+* Support horizon-spec-0.3.0
+* Allow for building from local packages and tarballs.
+
 ## v0.2
 
 * Support horizon-spec-0.2

horizon-gen-nix.cabal

 cabal-version:      3.0
 name:               horizon-gen-nix
-version:            0.2
+version:            0.3.0
 synopsis:           Generate nix expressions from horizon-spec definitions
 description:        Generate nix expressions from horizon-spec definitions
 category:           Package Management, Nix