Find 20 first StackOverflow users with a name

For this challenge build an app that connects to the StackExchange API and displays users as described below

Description

The following wireframes describe the screens for the app.
The ascii-drawings are for reference only.
Just make sure that the required data is displayed.

Main Screen

Display an input field and Button to search for users by name.
Display up to 20 users alphabetically and show their reputation and username.
When tapped, open a new Activity to display more information about the user.

+--------------------+
|  AppName           |
|--------------------+
| __________  SEARCH | - input and button  
| ------------------ |
| 123  Username1     |
| ------------------ |
| 390  Username2     | -----*tap* -----> user details screen
| ------------------ |
|   0  Username3     |
| ------------------ |
| 275  Username4     |
| ------------------ |
| 122  Username5     |
+--------------------+

User Details screen

Displays additional information about the user.

+--------------------+
| < User             | - up button and page title
|--------------------+
|                    |
|   +-----------+    |
|   |           |    |
|   |   Avatar  |    |
|   |           |    |
|   +-----------+    |
|   User Name        |
|   Reputation       |
|   Badges           |
|                    |
|   Location         |
|   Age              |
|   Creation Date    |
|                    |
+--------------------+

References

Retrofit2 - http://square.github.io/retrofit/
RxJava - https://github.com/ReactiveX/RxJava
StackExchange API - https://api.stackexchange.com/docs