Roll Observatory packages and add a roll script

packages/string_scanner/CHANGELOG.md

+## 0.1.4
+
+* Add `new SpanScanner.eager()` for creating a `SpanScanner` that eagerly
+  computes its current line and column numbers.
+
+## 0.1.3+2
+
+* Fix `LineScanner`'s handling of carriage returns to match that of
+  `SpanScanner`.
+
+## 0.1.3+1
+
+* Fixed the homepage URL.
+
+## 0.1.3
+
+* Add an optional `endState` argument to `SpanScanner.spanFrom`.
+
+## 0.1.2
+
+* Add `StringScanner.substring`, which returns a substring of the source string.
+
+## 0.1.1
+
+* Declare `SpanScanner`'s exposed `SourceSpan`s and `SourceLocation`s to be
+  `FileSpan`s and `FileLocation`s. They always were underneath, but callers may
+  now rely on it.
+
+* Add `SpanScanner.location`, which returns the scanner's current
+  `SourceLocation`.
+
+## 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