style(form): update border/spacing for input/select fields

BREAKING CHANGE: Because this impacts the layout/display of input and select fields,
it is recommended that a quick sanity check of forms in apps is done to ensure the
design still handles well.
style(rxForm): added white background to inputs
style(rxForm): fix size of radio/checkbox
Merge pull request #357 from rackerlabs/212-form-styles

Form style updates