Start index and length + AOSP-style buttons + Recently used tabs

I tested it a bit, it should work fine. I made this feature available only to TextViews.

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
This isn't follow singleton best practice. You may want to change it to:

```java
private static final Object LOCK = new Object();

public static EmojiconRecentsManager getInstance(Context context) {
    if (sInstance == null) {
        synchronize (LOCK) {
            if (sInstance == null) {
                 sInstance = new EmojiconRecentsManager(context);
            }
        }
    }
    return sInstance;
}
```