Change AccountService interface
Merge branch 'step-9' into step-10
Fix test error after merge
Merge branch 'step-10' into step-11
Simplify HomeControllerTest
Merge branch 'step-12' into step-13
Merge branch 'step-11' into step-12
Merge branch 'step-12' into step-13
Fix error after merge
Merge branch 'step-13' into step-14
Merge branch 'step-14' into step-15
Add rubycollect4j for AccountServiceImpl
Merge branch 'step-9' into step-10
Merge branch 'step-10' into step-11
Merge branch 'step-11' into step-12
Merge branch 'step-12' into step-13

Conflicts:
	pom.xml
Merge branch 'step-13' into step-14
Fix error after merge
Merge branch 'step-14' into step-15