docs(changelog.md): add 1.5.0-beta.0 entry
docs(changelog.md): add 1.5.0-beta.0 entry

This was a preparation release for the 1.5.x branch,
which only contains one fix over the previous 1.4.6
release.

Real-Currents/angular.js,Real-Currents/angular.js,Real-Currents/angular.js,Real-Currents/angular.js