docs(Table): add attached example

[layershifter]

This PR:

• fixes docs(Table): add attached example #595;
• adds test for attached prop to Table.

[codecov-io]

Current coverage is 100% (diff: 100%)

Merging #598 into master will not change coverage

@@           master   #598   diff @@
====================================
  Files         119    119          
  Lines        1915   1915          
  Methods         0      0          
  Messages        0      0          
  Branches        0      0          
====================================
  Hits         1915   1915          
  Misses          0      0          
  Partials        0      0          

Powered by Codecov. Last update 6c72147...3c541f2

[levithomason]

Thanks much, reviewing.

---

P.S. Based on how the changelog is categorizing labels, I'm going to start labeling issues/PRs like so:

• docs - for doc site changes (whether new docs, docs bug fix, or doc enhancement)
• enhancement - new library features
• bug - library bugs

[levithomason]

I changed the export from:

const TableCelled = () => {
  return (

To:

const TableExampleAttached = () => (

I also reduced the LOC from 104 to 42. I'd like to keep examples as small as possible for easier doc site usage.

Will ship when tests pass.