Add FollowingUsersFragment. closed #14

add fragment.
add menu_icon.
add item in drawer list.
Display list of users that follow, closed #15

- add APIManager.
- add Fragment.
The display on the ActionBar icon and name of the user.
Retrieve and display information for a specific user, closed #18

- create UserInfoAPIManager.
- create UserInfoFragment.
Create Fragment and APIManager.

- Display and acquisition of articles posted for a specific user, closed #19
- Display and acquisition of articles in stock for a specific user,
  closed #20
Merge branch 'feature/add-following-user-page' into develop