fix typo in metrics readme causing error (#32)

Summary:
Pull Request resolved: #32

In torchelastic/metrics/api.py the handler is called
ConsoleMetricHandler, but it is ConsoleMetricsHandler (note the extra "s") in the readme which could
cause confusion for users who try to run this code.

Differential Revision: D19456953

fbshipit-source-id: 83be603f27b59b14bbc694ed0b943b7de897c2f7

torchelastic/metrics/README.md

@@ -50,8 +50,8 @@ By adding the following configuration metrics in the `torchelastic` and
 ```python
 import torchelastic.metrics as metrics
 
-metrics.configure(metrics.ConsoleMetricsHandler(), group = "torchelastic")
-metrics.configure(metrics.ConsoleMetricsHandler(), group = "my_app")
+metrics.configure(metrics.ConsoleMetricHandler(), group = "torchelastic")
+metrics.configure(metrics.ConsoleMetricHandler(), group = "my_app")
 ``` 
 
 #### Implementing a Custom Metric Handler
@@ -77,4 +77,4 @@ Now all metrics in the group `my_app` will be printed to stdout as:
 ```
 [1574213883.4182858][my_app]: my_metric=<value>
 [1574213940.5237644][my_app]: my_metric=<value>
-```
+```