:art: Add isCommitSigned method
:art: Add isCommitSigned method

Add _isCommitSigned() to set the -s flag when the user prompt for Signed commit is yes.

Signed-off-by: Carlos Cuesta <cca07f2a9be1cdebff85325ea0add9602cfb1efc@me.com>

carloscuesta/gitmoji-cli,carloscuesta/gitmoji-cli