cssnext test for custom prop transformation

Custom

h1

h2

h1 .title

h2 .title

h1

h2

h1 .title

h2 .title

h1.title

h2.title

Transform

h1

h2

h1 .title

h2 .title

h1

h2

h1 .title

h2 .title

h1.title

h2.title