Bump minSdkVersion to 15.
Bump minSdkVersion to 15.

qiwx2012/DragLinearLayout,justasm/DragLinearLayout,dagezi/DragLinearLayout,mcaras/DragLinearLayout,HKMOpen/DragLinearLayout,DuongNTdev/DragLinearLayout,ly-android/DragLinearLayout,leasual/DragLinearLayout,msoftware/DragLinearLayout