Bumped Polymer version

[florianv]

When running bower install, there is a version conflict:

Unable to find a suitable version for polymer, please choose one:
    1) polymer#~0.3.4 which resolved to 0.3.5 and is required by seed-element 
    2) polymer#>=0.4.0 <1.0.0 which resolved to 0.4.0 and is required by core-component-page#0.4.0

If I choose the 0.3.5 version, I get an error when running the demo:

Uncaught TypeError: undefined is not a function
var declarations = Platform.deliverDeclarations();

Bumping Polymer version to 0.4.0 fixes the issues.

[florianv]

@ebidel Done.

[florianv]

I bumped the test-tools version too because >=0.3.3 <1.0.0 will currently resolve to 0.4.0.

[ebidel]

LGTM. Thanks!