Fix a spelling mistake (#21)
diff --git a/lib/src/stream_zip.dart b/lib/src/stream_zip.dart
index f9e2082..a65840c 100644
@@ -7,7 +7,7 @@
/// A stream that combines the values of other streams.
/// This emits lists of collected values from each input stream. The first list
-/// contains the first value emitted by each stream, the second contrains the
+/// contains the first value emitted by each stream, the second contains the
/// second value, and so on. The lists have the same ordering as the iterable
/// passed to [new StreamZip].