Add support for placeholder on type select#17

Merged

Anthropic merged 3 commits intojson-schema-form:developfrom

kornosaurus:select-placeholder

May 23, 2016

Commits on Mar 18, 2016

Support for placeholder key on select type
kornosaurus
committed
Better comments inside selectPlaceholder builder
kornosaurus
committed

Commits on Mar 21, 2016

$$value$$ could be something other than a string, like a boolean.. so we need to check if $$value$$ is undefined instead
kornosaurus
committed