Added library-level comments for polymer and polymer_expressions

pkg/polymer_expressions/lib/polymer_expressions.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+/**
+ * A syntax used with polymer elements that
+ * allows for complex binding expressions, including
+ * property access, function invocation,
+ * list/map indexing, and two-way filtering.
+ *
+ * Polymer expressions are part of the Polymer.dart project.

[sethladd, 2013/09/04 20:40:22]

I think it's one word: PolymerExpressions

[Jennifer Messerly, 2013/09/04 22:09:35]

so far we have been using two words in the readme:
http://pub.dartlang.org/packages/polymer_expressions

but I dunno if that's right.

@mem if you want to take a shot at fixing the README.md files too that would be
very welcome :)

[sethladd, 2013/09/04 22:21:15]

Looks like they updated their site.
http://www.polymer-project.org/docs/polymer/expressions.html  It's just
"expressions" now. So two words is fine. Good to know!

[mem, 2013/09/09 18:40:17]

I'll take a look at the README on Monday.

mem
On 2013/09/04 22:09:35, John Messerly wrote:

+ * Refer to the
+ * [Polymer.dart](http://www.dartlang.org/polymer-dart/)
+ * home page for example code, project status, and
+ * information about how to get started using Polymer.dart in your apps.
+ *
+ * To use the polymer_expressions package in your application,

[sethladd, 2013/09/04 20:40:22]

Is it useful to use polymer_expressions without polymer? maybe just say that you
get polymer_expressions when you install polymer.

[Jennifer Messerly, 2013/09/04 22:09:35]

It could be, if you are using data binding only.
But I agree -- it is better to give folks the "batteries included" complete
framework.

[mem, 2013/09/09 18:40:17]

Done.

+ * add a dependency in the app's pubspec.yaml file:
+ *
+ *     dependencies:
+ *       polymer_expressions: any
+ *
+ * Then import the library into your application:
+ *
+ *     import 'package:polymer_expressions/polymer_expressions.dart';
+ *
+ * ## Other resources
+ *
+ * * Check out the source code for the polymer expressions package

[sethladd, 2013/09/04 20:40:22]

you're not really checking out the source code at pub. How about "Learn more
about polymer_expressions package at pub ..."

[mem, 2013/09/09 18:40:17]

Done.

+ * at the pub repository:
+ * [polymer_expressions](http://pub.dartlang.org/packages/polymer_expressions).
+ *
+ * * If you were using Web UI in your apps,

[sethladd, 2013/09/04 20:40:22]

It's OK if you drop this, since we mention this on the polymer library doc.

[mem, 2013/09/09 18:40:17]

Done.

+ * [Upgrading to Polymer.dart]
+ * (http://www.dartlang.org/polymer-dart/upgrading-to-polymer-from-web-ui.html)
+ * contains some tips to help you convert.
+ */
+
 library polymer_expressions;
 
 import 'dart:async';
 import 'dart:html';
 
 import 'package:observe/observe.dart';
 
 import 'eval.dart';
 import 'expression.dart';
 import 'parser.dart';
@@ skipping 85 matching lines @@
 
   getValueWorkaround(key) {
     if (key == _VALUE) return value;
   }
 
   setValueWorkaround(key, v) {
     if (key == _VALUE) value = v;
   }
 
 }