Fix getMountableComponent type changing to React.SFC

[noisae]

In order to have more accurate type checking, we are changing the return of getMountableComponent toReact.SFC.

// getMountableComponent.js:17 returning a React.StatelessComponent
  return (props) => {
    return <ComponentInProvider {...props} />;
  };

[codecov]

Codecov Report

Merging #439 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #439   +/-   ##
=======================================
  Coverage   97.76%   97.76%           
=======================================
  Files         112      112           
  Lines        4386     4386           
=======================================
  Hits         4288     4288           
  Misses         98       98

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 78d9d0e...dfb38d5. Read the comment docs.