Small clean up in component instantiation

Review URL: https://chromiumcodereview.appspot.com//12386060
Fixes #369, incorrect type check in _matches
"is Text" didn't account for other node types, such as comments
https://github.com/dart-lang/web-ui/issues/369

Review URL: https://chromiumcodereview.appspot.com//12377069
fixes for latest sdk

File.name -> File.path
Arrays is private
fix ObservableList ctor

Review URL: https://chromiumcodereview.appspot.com//12385096
fix null ref in _fixImports when no-rewrite-urls is off

Review URL: https://chromiumcodereview.appspot.com//12463005
avoid using "library" psuedokeyword for local vars
workaround for https://github.com/dart-lang/dart-sublime-bundle/issues/11

Review URL: https://chromiumcodereview.appspot.com//12455010
bump pubspec
TBR

Review URL: https://chromiumcodereview.appspot.com//12435004
Unbreak clean command for libv2 .
Fix style nit.
Merge branch 'master' of https://github.com/dart-lang/web-ui into link_work
merged w/ lastest SDK