Change undesirable method name

Because it does not represent the difference between the contents of the method in the "modify" and "update".
Confirm github repository presence through github api
Tweak project form design

Tweak open range design
Merge pull request #102 from kmiyake/iss-98

プロジェクトへgithubレポジトリを登録する時にレポジトリの妥当性を確認する