Update browser dependency

[szgabsz91]

Hi!

I use your package with the polymer package, but running pub get with the latest version of polymer gives me the following error:

Incompatible version constraints on browser:
- animation depends on version >=0.9.0 <0.10.0
- polymer depends on version >=0.10.0 <0.11.0

Please, update your dependency version number to the browser package so that other packages can use the latest polymer package with animation.

Thanks in advance!