Bump controls version to 1.2.0#2017

Merged

jasongrout merged 8 commits intojupyter-widgets:masterfrom

jasongrout:version12

Mar 29, 2018

Commits on Mar 28, 2018

Add default semver range logic to the html widget manager too.
jasongrout
committed
Revert "Add default semver range logic to the html widget manager too."
jasongrout
committed
Special-case the new semver range logic to the Jupyter widgets base/controls packages.
jasongrout
committed