added clarity to schema:download (#475)

* added clarity to schema:download

Hopefully less pain moving from apollo-codegen.

* updated CLI to match docs

Author: mwarger

packages/apollo-cli/README.md

@@ -150,10 +150,11 @@ ARGUMENTS
 
 OPTIONS
   -h, --help           Show command help
-  --endpoint=endpoint  [default: http://localhost:4000/graphql] The URL of the server to fetch the schema from
+  --endpoint=endpoint  [default: http://localhost:4000/graphql] The URL of the server to fetch the schema from or path to ./your/local/schema.graphql
   --header=header      Additional headers to send to server for introspectionQuery
   --key=key            The API key for the Apollo Engine service
 ```
+Note: This replaces `apollo-codegen introspect-schema`.
 
 _See code: [src/commands/schema/download.ts](https://github.com/apollographql/apollo-cli/blob/v1.1.1/src/commands/schema/download.ts)_
 

packages/apollo-cli/src/commands/schema/download.ts

@@ -28,7 +28,7 @@ export default class SchemaDownload extends Command {
         "Additional headers to send to server for introspectionQuery",
     }),
     endpoint: flags.string({
-      description: "The URL of the server to fetch the schema from",
+      description: "The URL of the server to fetch the schema from or path to ./your/local/schema.graphql",
       default: "http://localhost:4000/graphql", // apollo-server 2.0 default address
     }),