add commit functionality to st create command

[blmalone]

A common git workflow goes something like this:

• create a branch
• check out the branch
• commit to the branch

Graphite combines this workflow into a useful command that I find myself using frequently:

gt create --all --message "commit message"
# the --all flag is defined as: Stage all unstaged changes before creating the branch, including to untracked files.

It would be cool if st provided the same funcitonality:

st create --all --message "commit message"

In the current version of st, I need to provide 4 commands to perform the same action:

st create my-branch 
git add . && git commit -m "my commit"
st submit # some additional button clicks here too