https://www.learn2crack.com/2016/09/android-user-registration-login-node-client.html
https://www.youtube.com/watch?v=5b0wWZuTazA
com.android.support:appcompat-v7:24.2.1
com.android.support:design:24.2.1
com.android.support:cardview-v7:24.2.1
com.squareup.retrofit2:retrofit:2.1.0
com.squareup.retrofit2:converter-gson:2.1.0
com.squareup.retrofit2:adapter-rxjava:2.1.0
io.reactivex:rxjava:1.2.0
io.reactivex:rxandroid:1.2.1