Bump version to 0.2-4

Release a new version including the upgraded commonmark and
prettify dependencies.

Change-Id: Iaba3da24da8e856a5b7e598b44ed1f7ff9f44b2e

version.bzl

diff --git a/version.bzl b/version.bzl
index e9e06fe..073d00a 100644
--- a/version.bzl
+++ b/version.bzl
@@ -4,4 +4,4 @@
 # we currently have no stable releases, we use the "build number" scheme
 # described at:
 # http://mojo.codehaus.org/versions-maven-plugin/version-rules.html
-GITILES_VERSION = "0.2-3"
+GITILES_VERSION = "0.2-4"