Do not update junit, guice or httpcomponents to alpha resp. beta versions.
PEP recommendations and close handles
Fixes #62: mvn versions:update-properties versions:use-latest-releases (maven-deploy-plugin, maven-install-plugin, guava, httpcomponents)

Updated ${maven-deploy-plugin.version} from 2.8.1 to 2.8.2
Updated ${maven-install-plugin.version} from 2.5.1 to 2.5.2
Updated ${guava.version} from 17.0 to 18.0
Updated org.apache.httpcomponents:httpclient:jar:4.3.3 to version 4.3.5
Updated org.apache.httpcomponents:httpclient-cache:jar:4.3.3 to version 4.3.5