Move theming into its own file

[emmatown]

⚠️ Breaking Change ⚠️

What:

Move ThemeProvider and withTheme exports to emotion/react/theming.

Why:

Because not everyone wants theming and this doesn't force people to include it if they don't want it.

How:

Checklist:

• Documentation
• Tests
• Code complete

[thangngoc89]

Yes. Yes. Yes. I'm upset about the size of emotion after adding theming feature

[codecov-io]

Codecov Report

Merging #130 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #130      +/-   ##
==========================================
+ Coverage   89.06%   89.08%   +0.01%     
==========================================
  Files          16       18       +2     
  Lines         631      632       +1     
  Branches      145      145              
==========================================
+ Hits          562      563       +1     
  Misses         56       56              
  Partials       13       13

Impacted Files	Coverage Δ
src/react/index.js	85.71% <ø> (ø)
src/react/theming.js	100% <100%> (ø)
src/react/constants.js	100% <100%> (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 c0e000a...a67aaf7. Read the comment docs.

[tkh44]

@mitchellhamilton I'm sitting on this until I figure out the glamor and className merging.