Checking in changes prior to tagging of version v0.12.3

v0.12.3 (2019-05-16)

• [fix] Ignore files which seems to system hidden file in walking #176 (Songmu)
• [fix] Fix the list if symlink is in the same directory #174 (at-grandpa)
• [refactoring] introduce Songmu/gitconfig #175 (Songmu)
• [refactoring] Get ghq.completeUser strictly as a boolean value #172 (Songmu)