Improve pid directory handling

fix security issue with mode 777 for pid directory
take default user for pid directory from config file
make pid handling configurable via /etc/default/newrelic_plugin_agent
catch Timeout exception
Merge pull request #236 from trbs/deb_init_piddir

Improve pid directory handling
Merge pull request #239 from trbs/timeout_exception

catch Timeout exception
Bump the release