Add an example of MetricRegistryFactory to the spec. Fixes #83
Add an example of MetricRegistryFactory to the spec. Fixes #83

Signed-off-by: Raymond Lam <2e5d8a94c9ccc6688abf58c82d675708bfd6dfb3@ca.ibm.com>

Channyboy/microprofile-metrics,Channyboy/microprofile-metrics,raymondlam/microprofile-metrics,Arjun-Sharma1/microprofile-metrics,raymondlam/microprofile-metrics,Arjun-Sharma1/microprofile-metrics,pilhuhn/microprofile-metrics,pilhuhn/microprofile-metrics