solve ch04/ex2
Merge branch 'master' into ex2

Conflicts:
	ch04/exercises.hs
safeHead_m, splitWith_mを作成
Merge pull request #1 from papamitra/ex2

solve ch04/ex2
改行追加
Merge branch 'master' of https://github.com/minddnim/RWH_EX into minddnim-master

Conflicts:
	ch04/exercises.hs
Merge remote-tracking branch 'upstream/master'