Instead of using spoiler boolean and spoiler_text, simply check for non-blank spoiler_text

Federate spoiler_text using warning attribute on <content /> instead of a <category term="spoiler" />
Clean up schema file from accidental development migrations

app/assets/javascripts/components/actions/compose.jsx

@@ -70,7 +70,6 @@ export function submitCompose() {
       in_reply_to_id: getState().getIn(['compose', 'in_reply_to'], null),
       media_ids: getState().getIn(['compose', 'media_attachments']).map(item => item.get('id')),
       sensitive: getState().getIn(['compose', 'sensitive']),
-      spoiler: getState().getIn(['compose', 'spoiler']),
       spoiler_text: getState().getIn(['compose', 'spoiler_text'], ''),
       visibility: getState().getIn(['compose', 'private']) ? 'private' : (getState().getIn(['compose', 'unlisted']) ? 'unlisted' : 'public')
     }).then(function (response) {