changelog update for 0.2.0 release (#363)

Author: david-koenig

CHANGELOG.rst

@@ -17,9 +17,10 @@ Changelog
 * Local tests only by default
 * Fix of MAP_ANONYMOUS issue for older Linuxes
 
-0.2.0 -- 2019-04-29
+0.2.0 -- 2019-05-13
 ===================
 * Added API function to make session from keyring
 * Added API function to make caching CMM from keyring
 * Added "_from_cmm" to end of "aws_cryptosdk_caching_cmm_new" function name
 * Changed "aws_cryptosdk_session_get_algorithm" to "aws_cryptosdk_session_get_alg_id"
+* Fixed HKDF bug