Fix for PLUG-177 released.

PLUG-177 - cpu_core plugin dies on error

Release 0.9.3

• Updated README with information on the change in the CPU Core indexing scheme from 1 to N prior to release 0.9.2 to 0 to N-1 in the 0.9.2 and later release
• Incremented the revision number in plugin.json to 0.9.3

Release version 0.9.2

Initial public release of lua version of the CPU Core plugin