v0.17.1

Overview

• Adds the batch operator to Dataflows. Calling Dataflow.batch
  will batch incoming items until either a batch size has been reached
  or a timeout has passed.

• Adds the SimplePollingInput source. Subclass this input source to
  periodically source new input for a dataflow.

• Re-adds GLIBC 2.27 builds to support older linux distributions.

What's Changed

• Batch operator by @Psykopear in #287
• Re-add glibc 2.27 builder by @whoahbot in #297
• PeriodicInput source by @Psykopear in #295
• Prepare for v0.17.1 release by @whoahbot in #299

Full Changelog: v0.17.0...v0.17.1