git prune-branches

@kevgo please review

+ Changed a couple git helpers to take in parameters instead of operating on the current branch
+ Set the default branch on the remote repo to main (needed as the git prune-branches feature specs were deleting the master branch (since its not main) and you cannot delete the HEAD branch on the remote repo.
Dynamic typing allows to make this more intuitive. Call it like this:

```ruby
create_commits branch: main
# or
create_commits [{ branch: main}, { branch: foo }]
```

This is implemented as 

```ruby
def create_commits options
# Convert options into an array
options = [options] unless options.is_a? Array

...
```