0.3: tagged by rultor.com

Added optional subscriber executor service

PR #35
Closes #34 - added optional executor service for subscriber of
read channel publisher, and other implementers. Refactored by moving
IO exec from parameter to field, using fork join pool as a default
instead of cached thread pool for enabling job stealing.

0.2.1: tagged by rultor.com

Merge pull request #5 from g4s8/4

Handle unchecked exceptions

#1 - readme fixes