Feature/release 0.1.4

[gtrinkwon]

Fixes:

• Set mapped to false by default for custom Html block type, to prevent the need to do so manually.
• Moved choice fieldset element from form_row_render to choice_widget_expanded to allow checkbox attributes to be added to fieldset. (solves issue where screen readers were not announcing errors on checkbox/radio focus)
• Fixed multiple validation errors for one field being listed as one error and appended to the same string.
• Appended _0 to the error block so that the first checkbox/radio is highlighted when clicking the error summary anchor.