Use cowsay from the PATH instead
vcsh: Initial support for cloning from branches other than master
vcsh: Proper quoting for "$VCSH_BRANCH"
vcsh: Create the local branch during clone

This will create and checkout a local branch named after the upstream
branch. It will also gracefully behave for the default `master' branch
and consistently show the same message:

Switched to a new branch '$VCSH_BRANCH'
vcsh: Only fetch the upstream branch during clone
vcsh: `vcsh clone [-b <branch>] <remote> [<repo>]`

This is the API for an optional branch selection for `vcsh clone`. It is
basically inspired by `git clone [-b|--branch <name>] <remote>`. I could
have used the long option `--branch` too but vcsh only uses short ones.
vcsh: Fail fast if the clone branch is not valid

Also fixed the last hardcoded reference to the master branch.
doc/vcsh.1.ronn: Document clone [-b `branch`]
permit "-b <branch>" to come later on the command line
Merge pull request #144 from mirabilos/patch-1

permit "-b <branch>" to come later on the command line
Merge branch 'feature--clone_branch'

Conflicts:
	vcsh