#6 日付追加
Revert "#6 日付追加"

This reverts commit 7e938f0304d31243c0237921560050321f527059.
Merge branch '#5' into develop
足し算引き算追加
Merge pull request #7 from f117karikari/#7

#7 足し算引き算追加
#8 エラー処理を追加
Merge pull request #8 from f117karikari/#8

#8 割り算の前提処理を追加
#10 計算結果をStringで返すように修正
Merge pull request #11 from f117karikari/master

Master
コンフリクト解消
Merge pull request #13 from f117karikari/#11

#11 足し算引き算追加
test5
test6
test7
test8
test9
test10
test11
test12
test is bad