Pull args, intl, logging, shelf, and source_maps out of the SDK.

pkg/source_maps/README.md

-Source Maps
-===========
-
-This project implements a Dart pub package to work with source maps. The
-implementation is based on the [source map version 3 spec][spec] which was
-originated from the [Closure Compiler][closure] and has been implemented in
-Chrome and Firefox.
-
-In this package we provide:
-
-  * Data types defining file locations and spans: these are not part of the
-    original source map specification. These data types are great for tracking
-    source locations on source maps, but they can also be used by tools to
-    reporting useful error messages that include on source locations.
-  * A builder that creates a source map programatically and produces the encoded
-    source map format.
-  * A parser that reads the source map format and provides APIs to read the
-    mapping information.
-
-Some upcoming features we are planning to add to this package are:
-
-  * A printer that lets you generate code, but record source map information in
-    the process.
-  * A tool that can compose source maps together. This would be useful for
-    instance, if you have 2 tools that produce source maps and you call one with
-    the result of the other.
-
-[closure]: http://code.google.com/p/closure-compiler/wiki/SourceMaps
-[spec]: https://docs.google.com/a/google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit