Add API modifiers to limit returned toots from public/hashtag timelines

to only those from local users; Add link to "extended information" to
getting started in the UI; Add defaults for posting privacy; Change
how publish button looks depending on posting privacy chosen

app/assets/javascripts/components/components/button.jsx

@@ -9,6 +9,7 @@ const Button = React.createClass({
     block: React.PropTypes.bool,
     secondary: React.PropTypes.bool,
     size: React.PropTypes.number,
+    children: React.PropTypes.node
   },
 
   getDefaultProps () {
@@ -38,7 +39,6 @@ const Button = React.createClass({
       fontSize: '14px',
       fontWeight: '500',
       letterSpacing: '0',
-      textTransform: 'uppercase',
       padding: `0 ${this.props.size / 2.25}px`,
       height: `${this.props.size}px`,
       cursor: 'pointer',