Updating TravisCI config to match the updated project config

Author: milosmns

.travis.yml

@@ -9,9 +9,9 @@ branches:
 # Setup environment variables
 env:
   global:
-    - PLATFORM_TOOLS=25.0.4
-    - BUILD_TOOLS=25.0.2
-    - COMPILE_SDK=25
+    - PLATFORM_TOOLS=27.0.1
+    - BUILD_TOOLS=27.0.3
+    - COMPILE_SDK=27
     - ADB_INSTALL_TIMEOUT=15 # Wait up to 15 minutes for adb to connect to the emulator
 
 # Enable only JDK 8, source does not build with JDK 7