Fix Issue #4
Fix Issue #5
Merge pull request #13 from yamanetoshi/Issue#4

Fix Issue #4
Merge pull request #14 from yamanetoshi/Issue#5

Fix Issue #5
Fix Issue #6
Merge branch 'master' into Issue#6

Conflicts:
	tutorial.md
Merge pull request #15 from yamanetoshi/Issue#6

Fix Issue #6
Merge branch 'master' into Issue#7

Conflicts:
	tutorial.md