Revert "Merge pull request #8 from 2014-Android-ITX4/#4-修正-背景を白色から桃色のグラデーションにする-"

This reverts commit 4d324a565d535877a9e5b9bb416d06e4eca51669, reversing
changes made to 6670c75870d8f659a7753c96b4e872d5d87f63fb.