update plugin and dependency versions

  - update plugin and dependency versions: not I only did a minor update of the maven-plugin-api (to 3.0.5 and not upgrade to 3.1.1)
  - fix a deprecation in ScriptCoverageStatistics; related to updating Guava
  - fix previously deprecated, now missing Proxy.setHttpsProxy(...) in GenericInstrumentingBrowser and InstrumentingProxyServerIT; related to updating Selenium
Merge pull request #109 from mprins/version-updates

update plugin and dependency versions