Add LineScanner and SpanScanner classes to string_scanner.

pkg/string_scanner/CHANGELOG.md

Index: pkg/string_scanner/CHANGELOG.md
diff --git a/pkg/string_scanner/CHANGELOG.md b/pkg/string_scanner/CHANGELOG.md
new file mode 100644
index 0000000000000000000000000000000000000000..2c41c9d6450e3932f26580807a4f6438f268d8c5
--- /dev/null
+++ b/pkg/string_scanner/CHANGELOG.md
@@ -0,0 +1,19 @@
+## 0.0.2
+
+* `new StringScanner()` now takes an optional `sourceUrl` argument that provides
+  the URL of the source file. This is used for error reporting.
+
+* Add `StringScanner.readChar()` and `StringScanner.peekChar()` methods for
+  doing character-by-character scanning.
+
+* Scanners now throw `StringScannerException`s which provide more detailed
+  access to information about the errors that were thrown and can provide
+  terminal-colored messages.
+
+* Add a `LineScanner` subclass of `StringScanner` that automatically tracks line
+  and column information of the text being scanned.
+
+* Add a `SpanScanner` subclass of `LineScanner` that exposes matched ranges as
+  [source map][] `Span` objects.
+
+[source_map]: http://pub.dartlang.org/packages/source_maps