Add a --reporter flag and expose the expanded reporter.

lib/src/runner/reporter/compact.dart

Index: lib/src/runner/reporter/compact.dart
diff --git a/lib/src/runner/reporter/compact.dart b/lib/src/runner/reporter/compact.dart
index 2c1e8716095dba0f804e9a3a6cbccb00e188190b..5440c1a678625b572fb1fda60afc6e7b5865fb26 100644
--- a/lib/src/runner/reporter/compact.dart
+++ b/lib/src/runner/reporter/compact.dart
@@ -86,8 +86,8 @@ class CompactReporter {
 
   /// Creates a [ConsoleReporter] that will run all tests in [suites].
   ///
-  /// If [color] is `true`, this will use terminal colors; if it's `false`, it
-  /// won't.
+  /// [concurrency] controls how many suites are run at once. If [color] is
+  /// `true`, this will use terminal colors; if it's `false`, it won't.
   CompactReporter(Iterable<Suite> suites, {int concurrency, bool color: true})
       : _multiplePaths = suites.map((suite) => suite.path).toSet().length > 1,
         _multiplePlatforms =