Replace `componentWillMount`

[roccoluke]

We use v1 and would remain using it but prefer if we can fix the warning regards using componentWillMount. Do you intend to fix or will you accept a PR to replace it with componentDidMount?

react-frontload/src/index.js

Line 193 in c941d89

this.componentWillMount = this.pushFrontload(LIFECYCLE_PHASES.MOUNT)