updated to r20259
updated to dart build r20259
Update pubspec.yaml

The newer browser packages should always be fine for us.
Update xml_element.dart

changed addChildren from addChildren(Collection<XmlNode> elements) to https://github.com/prujohn/dart-xml/issues/21. 

however attempt to run the unit tests through dart m4 threw a number of other faults in 
Unhandled exception:
'package:unittest/unittest.dart': Error: line 788 pos 28: type 'ExpectException' is not loaded
    String message = (e is ExpectException) ? e.message : 'Caught $e';

I have no idea what is happening ... 
Sorry but I am new in this ...
Merge pull request #22 from nickfloros/master

attempt to fix issue 21
update pubspec ver
Upgrade to unittest 0.5.5
Update library to use Dart 0.5.5 APIs

- Use Iterable in place of Collection.
- Replace missing collection API methods, i.e. removeAll(), retainAll().
- Use if/else in place of switch statements when evaluating non-constants.
- Replace usage of List.getRange() with List.skip().take().

All tests are passing.
Merge pull request #26 from danschultz/upgrade_to_dart_0.5.5

Upgrade to Dart 0.5.5
advance version
updated AUTHORS file
Fix for invalid XML exception with namespaces

See https://github.com/prujohn/dart-xml/issues/10.
Fix syntax error with documentation
Stop whitespace trimming in attributes

Changes:
* Now entire inside of a quote is now tokenized

Testing:
* Made test for new behavior, fixed broken ones
Make isInTag private
Make static const, reported as error in dart editor
Add missing interfaces
Merge pull request #33 from financeCoding/minor_fixes

Minor fixes
Merge pull request #31 from ajlai/fix/stop-whitespace-trimming-in-attributes

Stop whitespace trimming in attributes
Merge pull request #28 from danschultz/fix-namespace-parsing-error

Fix for invalid XML exception with namespaces