Add a setup.cfg keywords to describe taskflow

Include keywords that will be searchable on
pypi (and any indexing sites) that describe
in single words what taskflow is all about.

Change-Id: I8971707044e92e330fed73c485f10ecd5244445f

setup.cfg

@@ -6,6 +6,10 @@ description-file =
 author = Taskflow Developers
 author-email = taskflow-dev@lists.launchpad.net
 home-page = https://launchpad.net/taskflow
+keywords = reliable recoverable execution
+           tasks flows workflows jobs
+           persistence states
+           asynchronous parallel threads
 classifier =
     Development Status :: 4 - Beta
     Environment :: OpenStack