Test case for additional issue with #69

Test case for the column headers in the *second* table polluting the
columns in the *first* instead of the other way around
Fix code style

Get rid of pointless comments and make braces same-line.
Test column headers in non-mounted DOM nodes

The pollution of HTML between the DOM nodes here wasn't actually
React's fault, instead it looks like it was caused by mounting the test
`<div>`s in the DOM. Doing it as non-mounted nodes fixes #69.
Merge pull request #74 from glittershark/69/fix-multiple-per-page-again

Test multiple tables in non-mounted DOM nodes
Don't call toString() on React component children

Don't call `toString()` on children of the <Td> if they're React
components

To check if a variable is a react component this just tests if
`typeof(thing.props) !== 'undefined'`, which is hacky and not very
robust, and a serious case for improvement.

Fixes #76