feat(Icon|Flag): PureComponent for Icon/Flag

[brianespinosa]

Per comments here, I have added in support for PureComponent in Icon and Flag. It looks like since that discussion happened last, someone has already added support for SCU and shallowEqual so adding PureComponent was the last piece for this.

[codecov-io]

Codecov Report

Merging #2067 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2067   +/-   ##
=======================================
  Coverage   99.76%   99.76%           
=======================================
  Files         149      149           
  Lines        2588     2588           
=======================================
  Hits         2582     2582           
  Misses          6        6

Impacted Files	Coverage Δ
src/elements/Flag/Flag.js	87.5% <ø> (ø)	⬆️
src/elements/Icon/Icon.js	100% <ø> (ø)	⬆️

---

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 d288f3b...20d08a5. Read the comment docs.

[layershifter]

@brianespinosa Thanks for the contribution, but we can't merge it. I've done these changes in #2011, in fact this equal to the PureComponent:

  shouldComponentUpdate(nextProps) {
    return !shallowEqual(this.props, nextProps)
  }

We also support range of react vesions, while PureComponent was introduced in 15.3.

[brianespinosa]

ha thanks @layershifter it took me so long to get to the updates that you beat me to it.