fontFamily, fontStyle and fontWeight support for TextInput

Summary:
fontFamily, fontWeight and fontStyle properties are being ignored for TextInput.

There's an additional issue that happens when you add secureTextEntry={true}  it overrides the current font preferences (because it defaults to monospace) so we have to reapply it.
Master right now:

![screen shot 2016-03-21 at 6 21 05 pm](https://cloud.githubusercontent.com/assets/1247834/13936110/c25ffea8-ef91-11e5-8d71-1b0a55184e24.png)

Demo after the fix:

![5ux4bpjfwh](https://cloud.githubusercontent.com/assets/1247834/13935865/0f2ca8be-ef90-11e5-82c7-d5a2dd33b70e.gif)
Closes https://github.com/facebook/react-native/pull/6564

Differential Revision: D3081623

Pulled By: bestander

fb-gh-sync-id: 329cac6755b5a0dd549e546768f39efa7b7f4daa
fbshipit-source-id: 329cac6755b5a0dd549e546768f39efa7b7f4daa

Examples/UIExplorer/TextInputExample.android.js

@@ -407,6 +407,31 @@ exports.examples = [
       );
     }
   },
+  {
+    title: 'fontFamily, fontWeight and fontStyle',
+    render: function() {
+      return (
+        <View>
+          <TextInput 
+            style={[styles.singleLine, {fontFamily: 'sans-serif'}]}
+            placeholder="Custom fonts like Sans-Serif are supported"
+          />
+          <TextInput 
+            style={[styles.singleLine, {fontFamily: 'sans-serif', fontWeight: 'bold'}]}
+            placeholder="Sans-Serif bold"
+          />
+          <TextInput 
+            style={[styles.singleLine, {fontFamily: 'sans-serif', fontStyle: 'italic'}]}
+            placeholder="Sans-Serif italic"
+          />
+          <TextInput 
+            style={[styles.singleLine, {fontFamily: 'serif'}]}
+            placeholder="Serif"
+          />
+        </View>
+      );
+    }
+  },
   {
     title: 'Passwords',
     render: function() {