minor usage and readme fixes

USAGE.md

 # Usage
 
 The [Dart Dev Compiler](README.md) (DDC) is an **experimental**
 development tool and transpiler.  In particular, the ES6 backend is
 still incomplete, under heavy development, and not yet ready for
 production use.
 
 With those caveats, we welcome feedback.  
 
 ## Installation
@@ skipping 14 matching lines @@
 void main() {
   List<String> list = ["hello", "world"];
 
   for (var item in list) {
     print(item + 42);
   }
 }
 ```
 
 the Dart analyzer will not report a static error or warning even
-though the program will clearly fail (in checked mode).  Running DDC:
+though the program will clearly fail (in checked mode).  Running with --strong
+mode:
 
-    $ dartdevc main.dart
+    $ dartanalyzer --strong main.dart
 
 will display a severe error.  Modifying `42` to `'42'` will
 correct the error.
 
 ## Generating ES6
 
 For code that statically type checks, DDC can be used to generate EcmaScript 6 (ES6) code:
 
     $ dartdevc -o out main.dart
 
@@ skipping 24 matching lines @@
 an example.
 
 ## Feedback
 
 Please file issues in our [GitHub issue tracker](https://github.com/dart-lang/dev_compiler/issues).
 
 You can also view or join our [mailing list](https://groups.google.com/a/dartlang.org/forum/#!forum/dev-compiler).