Although Github reserves the 'visionmedia' user space(a visit to there
will be redirected to 'tj'), it's better to
rename the links from visionmedia/git-extras to tj/git-extras
Added -s --soft arguments as well.
Default roll-back one with HEAD^ and only using ~ if commit count more than 1.
Added auto complete.
Updated documentation.
Attitude adjustment: don't throw errors and say NO as suggested in #114, have a can do attitude instead, leave the errors up to git to report.
-h option allows you to undo the last commit without keeping the
changes in the local working directory. Use with care.
Updated documentation to include new option.