Use 1 as the default number of commits (git last)

This patch sets the default number of commits to 1, in case
no number of commits is specified on the command line (note
that this requires the bash shell, as it uses bash-specific
shell parameter expansion syntax)... avoiding the following
error message:

~ $ git last
error: -n requires an argument
~ $ git-last
error: -n requires an argument
~ $ _
Merge pull request #13 from simplybusiness/git_last_number_of_commits

Use 1 as the default number of commits (git last)
update git-wtf to handle branches with '/' in them, like git-flow 'feature/feature-name' branches
Merge pull request #14 from korishev/master

make git-wtf handle branches with a '/' in them
git-wtf: Change delimiter of `git log --pretty` format string to |.

This prevents e-mail addresses with dashes in them from mangling the
output of the command. | is a safer character than , because it cannot
appear in e-mail addresses or commit IDs.
Merge pull request #18 from brantb/master

git-wtf: Change delimiter of `git log --pretty` format string to |.
unwip: check previous commit
Closes #15
Merge pull request #20 from phoenixsong6/unwip

unwip: check previous commit