Fixed text background color

Summary:
@public

This fixes an issue with the containerBackgroundColor property of `<Text>` nodes, where containerBackgroundColor was being overridden by the backgroundColor. I also fixed up the example so that it demonstrates the feature more clearly.

Test Plan:
* Check UIExplorer text example
* Run Catalyst snapshot tests and check MAdMan, Groups

Examples/UIExplorer/TextExample.ios.js

@@ -300,17 +300,17 @@ exports.examples = [
   title: 'containerBackgroundColor attribute',
   render: function() {
     return (
-      <View>
-        <View style={{flexDirection: 'row', height: 85}}>
-          <View style={{backgroundColor: '#ffaaaa', width: 150}} />
-          <View style={{backgroundColor: '#aaaaff', width: 150}} />
+      <View style={{backgroundColor: 'yellow'}}>
+        <View style={{flexDirection: 'row', position: 'absolute', height: 80}}>
+          <View style={{backgroundColor: '#ffaaaa', width: 140}} />
+          <View style={{backgroundColor: '#aaaaff', width: 140}} />
         </View>
-        <Text style={[styles.backgroundColorText, {top: -80}]}>
+        <Text style={styles.backgroundColorText}>
           Default containerBackgroundColor (inherited) + backgroundColor wash
         </Text>
         <Text style={[
           styles.backgroundColorText,
-          {top: -70, containerBackgroundColor: 'transparent'}]}>
+          {marginBottom: 5, containerBackgroundColor: 'transparent'}]}>
           {"containerBackgroundColor: 'transparent' + backgroundColor wash"}
         </Text>
       </View>
@@ -322,13 +322,13 @@ exports.examples = [
     return (
       <View>
         <Text numberOfLines={1}>
-          Maximum of one line no matter now much I write here. If I keep writing it{"'"}ll just truncate after one line
+          Maximum of one line, no matter how much I write here. If I keep writing, it{"'"}ll just truncate after one line.
         </Text>
         <Text numberOfLines={2} style={{marginTop: 20}}>
-          Maximum of two lines no matter now much I write here. If I keep writing it{"'"}ll just truncate after two lines
+          Maximum of two lines, no matter how much I write here. If I keep writing, it{"'"}ll just truncate after two lines.
         </Text>
         <Text style={{marginTop: 20}}>
-          No maximum lines specified no matter now much I write here. If I keep writing it{"'"}ll just keep going and going
+          No maximum lines specified, no matter how much I write here. If I keep writing, it{"'"}ll just keep going and going.
         </Text>
       </View>
     );
@@ -337,7 +337,8 @@ exports.examples = [
 
 var styles = StyleSheet.create({
   backgroundColorText: {
-    left: 5,
+    margin: 5,
+    marginBottom: 0,
     backgroundColor: 'rgba(100, 100, 100, 0.3)'
   },
   entity: {