Issue #38 - Trigger Jenkins when a pull request is updated
Applied checkstyle constraints to new code contributed
Refactored out the PullRequestRescopeEvent into its own listener
Small tweak to Javadoc of RepositoryChangeListener
Refactored eligibility filters to use a common EventContext

This EventContext allows the filters to have only a single method that
needs to implementation.
Updated pom to 2.1.0-SNAPSHOT
Updated README release notes