Build: Upgrade to commitplease 1.11.0

commitplease had a bug before 1.9.0 where it didn't properly handle the
verbose flag `git commit -v`.

https://github.com/jzaefferer/commitplease/pull/19#issuecomment-45204680

This would lead to git diff for preview getting subjected to commit
message validation, which could abort commits if it failed.

Closes #679