docs: Update default resolver comment in README.md example (#78)

per: https://github.com/reactjs/react-docgen/blob/master/src/main.js#L18

Author: vpicone

README.md

@@ -103,7 +103,7 @@ So, we allow you to collect all the docgen info into a global collection. To do
       "babel-plugin-react-docgen",
       {
         "DOC_GEN_COLLECTION_NAME": "MY_REACT_DOCS",
-        "resolver": "findAllComponentDefinitions", // optional (default: findAllComponentDefinitions)
+        "resolver": "findAllComponentDefinitions", // optional (default: findAllExportedComponentDefinitions)
         "removeMethods": true, // optional (default: false)
         "handlers:": ["react-docgen-deprecation-handler"] // optional array of custom handlers (use the string name of the package in the array)
       }