Look at more of changelog to find version number

The introduction in CHANGELOG.md has grown larger since towncrier was
introduced, it is no longer good enough to look only at the first 10
lines to find the latest version.

version.sh

@@ -29,7 +29,7 @@ get_version() {
 }
 
 get_version_from_changelog() {
-    head -n10 CHANGELOG.md | awk '/^## \[[0-9]/ { print $2 }' | tr -d '[]'
+    head -n15 CHANGELOG.md | awk '/^## \[[0-9]/ { print $2 }' | tr -d '[]'
 }
 
 git_tag_exists() {