Theme custom prop

[ItsJonQ]

Theme custom prop

This update fixes the issue where a theme prop passed into the component
would be overridden by ThemeProvider.

The fix was to change the order of operations for supplying the theme prop to styled:

props.theme || (state !== null && state.theme) || {},

Storybook example below:

stories.add('The theme prop', () => {
  // Define our button
  const Button = styled('button')`
    font-size: 1em;
    margin: 1em;
    padding: 0.25em 1em;
    border-radius: 3px;

    /* Color the border and text with theme.main */
    color: ${props => props.theme.main};
    border: 2px solid ${props => props.theme.main};
  `

  // Define what main theme will look like
  const theme = {
    main: 'mediumseagreen',
  }

  return (
    <div>
      <Button theme={{main: 'royalblue'}}>Ad hoc theme</Button>
      <ThemeProvider theme={theme}>
        <div>
          <Button>Themed</Button>
          <Button theme={{main: 'darkorange'}}>Overidden</Button>
        </div>
      </ThemeProvider>
    </div>
  )
})

[coveralls]

Pull Request Test Coverage Report for Build 197

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 196:	0.0%
Covered Lines:	73
Relevant Lines:	73

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💛 - Coveralls