Add appengine/gcloud/mustache dependencies.

pkg/mustache/README.md

+# Mustache templates
+
+A Dart library to parse and render [mustache templates](http://mustache.github.com/mustache.5.html).
+
+[![Build Status](https://drone.io/github.com/xxgreg/mustache/status.png)](https://drone.io/github.com/xxgreg/mustache/latest)
+
+## Example
+```dart
+        import 'package:mustache/mustache.dart' as mustache;
+
+        main() {
+                var source = '{{#names}}<div>{{lastname}}, {{firstname}}</div>{{/names}}';
+                var template = mustache.parse(source);
+                var output = template.renderString({'names': [
+                        {'firstname': 'Greg', 'lastname': 'Lowe'},
+                        {'firstname': 'Bob', 'lastname': 'Johnson'}
+                ]});
+                print(output);
+        }
+```
+
+## API
+
+```dart
+
+Template parse(String source, {bool lenient : false});
+
+abstract class Template {
+        String renderString(values, {bool lenient : false, bool htmlEscapeValues : true});
+        void render(values, StringSink sink, {bool lenient : false, bool htmlEscapeValues : true});
+}
+
+```
+
+Once a template has been created it can be rendered any number of times.
+
+Both parse and render throw a FormatException if there is a problem with the template or rendering the values.
+
+When lenient mode is enabled tag names may use any characters, otherwise only a-z, A-Z, 0-9, underscore and minus. Lenient mode will also silently ignore nulls passed as values.
+
+By default all variables are html escaped, this behaviour can be changed by passing htmlEscapeValues : false.
+
+
+## Supported 
+```
+ Variables             {{var-name}}
+ Sections              {{#section}}Blah{{/section}}
+ Inverse sections      {{^section}}Blah{{/section}}
+ Comments              {{! Not output. }}
+ Unescaped variables   {{{var-name}}} and {{&var-name}}
+```
+See the [mustache templates tutorial](http://mustache.github.com/mustache.5.html) for more information.
+
+Passing all [mustache specification](https://github.com/mustache/spec/tree/master/specs) tests for interpolation, sections, inverted, comments. The following sections are not implemented: partials, lambdas and delimeters.
+
+## To do
+```
+Lenient nulls in inverse sections - see commented out test.
+Partial tags   {{>partial}}
+Allow functions as values (Lambdas)
+Set Delimiter tags
+```
+