Revert "Revert "Add in additional http request types""

This reverts commit 9e5c44f22b47fcb0d37c7b10de3b5db542424fa5.

Also, to run tests, the android:targetPackage in the
<instrumentation>needs to be set to
com.android.volley.tests (i.e., the volley_tests apk itself) because
volley is just a jar that is statically linked into the test apk.

Change-Id: I41ad41e401084b79fbf9712e24d7f7fdeb358223
diff --git a/Android.mk b/Android.mk
index 553eae8..c646b6d 100644
--- a/Android.mk
+++ b/Android.mk
@@ -28,5 +28,6 @@
 # TODO: Not yet.
 #$(call dist-for-goals, dist_files, $(LOCAL_BUILT_MODULE):volley.jar)
 
-# TODO: Build the tests as an APK here
+# Include build files in subdirectories
+include $(call all-makefiles-under,$(LOCAL_PATH))