Update Angular to use package:observable

[tvolkert]

No description provided.

[matanlurey]

LGTM, Approval.

[matanlurey]

@tvolkert I am seeing a pub error:

Package observe has no versions that match >=0.14.0 <0.15.0 derived from:
- angular depends on version ^0.14.0

@rkirov or @vsavkin can you help Todd merge this?

[tvolkert]

Weird - https://pub.dartlang.org/packages/observe is on version 0.14.0

[tvolkert]

Looks like this needs to wait until an update to polymer is published

dart-archive/polymer-expressions#9
dart-archive/polymer-dart#715

[tvolkert]

Actually, the problem seems to be with the introduction of the dependency on package:test (via package:observable and package:observe).

[tvolkert]

wtf?

$ pub get
Resolving dependencies... (2.7s) 
Package test has no versions that match >=0.12.3 <0.13.0 derived from:
- angular depends on version any
- code_transformers 0.3.1 depends on version >=0.12.1 <0.13.0
- guinness2 0.0.3 depends on version ^0.12.3

[tvolkert]

Huh, I actually get the following error trying to run pub get in against head...

$ pub get
Resolving dependencies... (10.6s) 
Package test has no versions that match >=0.12.3 <0.13.0 derived from:
- code_transformers 0.3.1 depends on version >=0.12.1 <0.13.0
- guinness2 0.0.3 depends on version ^0.12.3

[tvolkert]

There's a version tangle here that I don't have time to work through. If someone wants to land this PR, they'll have to update some version dependencies in pubspec.yaml

[matanlurey]

I think it's OK to keep Angular Dart 1 using the deprecated package for the time being - we aren't expecting any new users and old users are moving to Angular Dart 2.