message: bg => scheme in examples
diff: @@ -240,16 +240,16 @@ const Index = props => (
  <Box mb={4}>
  <Heading.h2 mb={1}>By color</Heading.h2>
  <Box mb={2}>
  - <StateLabel bg='invalid'>Invalid</StateLabel>
  + <StateLabel scheme='invalid'>Invalid</StateLabel>
  </Box>
  <Box mb={2}>
  - <StateLabel bg='green'>Green</StateLabel>
  + <StateLabel scheme='green'>Green</StateLabel>
  </Box>
  <Box mb={2}>
  - <StateLabel bg='red'>Red</StateLabel>
  + <StateLabel scheme='red'>Red</StateLabel>
  </Box>
  <Box mb={2}>
  - <StateLabel bg='purple'>Purple</StateLabel>
  + <StateLabel scheme='purple'>Purple</StateLabel>
  </Box>
  </Box>
  <Box mb={4}>
  @@ -276,19 +276,19 @@ const Index = props => (
  <Heading.h2 mb={1}>Small, by color</Heading.h2>
  <Box mb={2}>
  <span className='mr-2'>
  - <StateLabel small bg='invalid'>Invalid</StateLabel>
  + <StateLabel small scheme='invalid'>Invalid</StateLabel>
  </span>
  <span className='mr-2'>
  - <StateLabel small bg='green'>Green</StateLabel>
  + <StateLabel small scheme='green'>Green</StateLabel>
  </span>
  <span className='mr-2'>
  - <StateLabel small bg='red'>Red</StateLabel>
  + <StateLabel small scheme='red'>Red</StateLabel>
  </span>
  <span className='mr-2'>
  - <StateLabel small bg='purple'>Purple</StateLabel>
  + <StateLabel small scheme='purple'>Purple</StateLabel>
  </span>
  <span className='mr-2'>
  - <StateLabel small bg='green' icon={<Octicon name='git-branch'/>}>
  + <StateLabel small scheme='green' icon={<Octicon name='git-branch'/>}>
  Custom Octicon
  </StateLabel>
  </span>
  