The ability to create a signature has been added to Google's Inbox.
To create a signature login to Google Inbox, click the 3 lines to expand your navigation (if needed), then scroll down past your labels to the bottom of the column:
At the bottom of the navigation column, click Settings:
On the settings page, click Signature, move the slider button to On, and then type in your signature:
When you are done typing your signature click the Done link on the bottom right of the window.
Your new signature will be automatically synced across all of your devices.
To create a signature login to Google Inbox, click the 3 lines to expand your navigation (if needed), then scroll down past your labels to the bottom of the column:
At the bottom of the navigation column, click Settings:
On the settings page, click Signature, move the slider button to On, and then type in your signature:
When you are done typing your signature click the Done link on the bottom right of the window.
Your new signature will be automatically synced across all of your devices.