Bump version

Author: jamesnvc

pack.pl

@@ -1,6 +1,6 @@
 name(http2_client).
 title('An HTTP/2 client').
-version('0.3.0').
+version('0.4.0').
 author('James N. V. Cash', 'james.cash@occasionallycogent.com').
 home('https://gitlab.com/jamesnvc/prolog_http2_client').
 download('https://github.com/jamesnvc/http2_client/releases/*.zip').