version bump

CHANGELOG.md

 Changelog is kept at [GitHub](https://github.com/Dronehub/minijson/releases),
 here's only the changelog for the version in development
 
-# v2.1
-
-* proofed against loading empty strings
-* Python 3.6 is supported
-* minor speed improvements
+# v2.2

setup.cfg

 # coding: utf-8
 [metadata]
-version = 2.1
+version = 2.2a1
 name = minijson
 long-description = file: README.md
 long-description-content-type = text/markdown; charset=UTF-8