Add custom input render prop

[i-like-robots]

This adds a new renderInput prop to enable a custom input component to be provided.

function CustomInput({ classNames, inputWidth, ...inputProps }) {
  return <input className={classNames.input} style={{ width: inputWidth }} {...inputProps} />
}

[coveralls]

Pull Request Test Coverage Report for Build 4403268597

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 28 of 28 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 98.005%

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Totals
Change from base Build 4193674661:	0.02%
Covered Lines:	1330
Relevant Lines:	1356

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💛 - Coveralls