Add appengine/gcloud/mustache dependencies.

pkg/mustache/lib/mustache.dart

+library mustache;
+
+import 'dart:mirrors';
+
+part 'char_reader.dart';
+part 'scanner.dart';
+part 'template.dart';
+
+/// [Mustache template documentation](http://mustache.github.com/mustache.5.html)
+
+/// Returns a [Template] which can be used to render the mustache template 
+/// with substituted values.
+/// Tag names may only contain characters a-z, A-Z, 0-9, underscore, and minus,
+/// unless lenient mode is specified.
+/// Throws [FormatException] if the syntax of the source is invalid.
+Template parse(String source,
+                     {bool lenient : false}) => _parse(source, lenient: lenient);
+
+/// A Template can be rendered multiple times with different values.
+abstract class Template {
+        /// [values] can be a combination of Map, List, String. Any non-String object
+        /// will be converted using toString(). Null values will cause a 
+        /// FormatException, unless lenient module is enabled.
+        String renderString(values, {bool lenient : false, bool htmlEscapeValues : true});
+
+        /// [values] can be a combination of Map, List, String. Any non-String object
+        /// will be converted using toString(). Null values will cause a 
+        /// FormatException, unless lenient module is enabled.
+        void render(values, StringSink sink, {bool lenient : false, bool htmlEscapeValues : true});
+}
+
+/// MustacheFormatException is used to obtain the line and column numbers
+/// of the token which caused parse or render to fail.
+class MustacheFormatException implements FormatException {      
+        final String message;
+
+        /// The 1-based line number of the token where formatting error was found.
+        final int line;
+
+        /// The 1-based column number of the token where formatting error was found.
+        final int column;
+
+        MustacheFormatException(this.message, this.line, this.column);
+        String toString() => message;
+}