Move a number of packages and some of pub over to using source_span.

pkg/string_scanner/CHANGELOG.md

+## 0.1.0
+
+* Switch from `source_maps`' `Span` class to `source_span`'s `SourceSpan` class.
+
+* `new StringScanner()`'s `sourceUrl` parameter is now named to make it clear
+  that it can be safely `null`.
+
+* `new StringScannerException()` takes different arguments in a different order
+  to match `SpanFormatException`.
+
+* `StringScannerException.string` has been renamed to
+  `StringScannerException.source` to match the `FormatException` interface.
+
 ## 0.0.3
 
 * Make `StringScannerException` inherit from source_map's
   [`SpanFormatException`][].
 
 [SpanFormatException]: (http://www.dartdocs.org/documentation/source_maps/0.9.2/index.html#source_maps/source_maps.SpanFormatException)
 
 ## 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