Updated polymerapp for latest packages

Polymer < 0.15.4 returns warnings during build.

switch to the new travis dart configuration

Updated polymerapp template for polymer 0.15.5 and paper_elements
0.6.1. The template now uses key-up event because valueChanged was not
working with the latest paper_elements package.

update the version of usage that we depend on

0.1.5+2

Add web tests

Test that project generation can work from a dart:html environment.

add gitignore to appengineapp and cleanup

move stagehand over to using the usage GA library

Tweak CHANGELOG.md

sort file listings

--version checks latest version