This updates to mojo 4e4d51ce28a and mojo sdk 711a0bcfb141b4 and updates the sky
package's pubspec.yaml dependency to '>=0.1.0 <0.2.0' to be compatible with
the current mojo package. This includes an update to the Mojo Dart generator to
produce real classes for enums and the corresponding updates for users of the
KeyboardType enum in Sky as well as one scoped_ptr->std::unique_ptr in shell
corresponding to a change in the Mojo EDK.

When a new version of the sky and sky_services package are pushed this will fix
domokit/mojo#440.

This code is now part of sky_tools.

Also, add an example for the date picker

This patch adds a new test harness and a first, trivial test to run with the
harness. The new test harness is built on package:test and should run on
Travis. Over time, we'll migrate our existing tests into this harness.

@abarth