Fix spelling error (#259)

Author: krtk6160

README.md

@@ -178,7 +178,7 @@ This command compares the manifests details of a named release.
 
 It can be used to compare the manifests of 
  
- - lastest REVISION with specified REVISION
+ - latest REVISION with specified REVISION
 	$ helm diff revision [flags] RELEASE REVISION1
    Example: 
 	$ helm diff revision my-release 2