Drop support for kitkat; Bump minSdk to 21

This has been dead for a while already, remove the code and bump minSdk to a
version that actually works

Signed-off-by: Aayush Gupta <aayushgupta219@gmail.com>

app/src/main/res/drawable/divider_line.xml

@@ -19,7 +19,8 @@
 
 <shape xmlns:android="http://schemas.android.com/apk/res/android"
     android:shape="rectangle">
+    <solid android:color="?colorAccent" />
     <size
-        android:width="1dp"
+        android:width="1.25dp"
         android:height="12dp" />
 </shape>