Cleanup of zsh-dwim

Cleanup of zsh-dwim

I went ahead and cleaned up [zsh-dwim](https://github.com/oknowton/zsh-dwim) (Do What I Mean) quite a bit. If you haven't been following along, [zsh-dwim](https://github.com/oknowton/zsh-dwim) attempts to predict your intended next command when you hit `control-u`. I also recorded a short screen cast demonstrating some of what happens when you hit `control-u`.\n\n\n\n## Removing the Perl dependency\n\nI decided that I may as well bite the bullet and move all the transformation logic to `zsh` from the original Perl \"helper\" script. Early on, I was worried that `zsh` code would be too ugly, but I have too many ideas that would be hard to implement with the code base split up like that.\n\nAll the transformation logic now uses `zsh` and `sed`. I was hoping to use `zsh`'s built-in substitution abilities, but they were lacking some important features. The \"scp to mv\" transformation looked like it would have been really ugly without `sed`.\n\n## Cleaning up the if/then spaghetti\n\nWhen I was testing this idea I only had two transformations, so a pair of if/then statements didn't seem like a problem. Now that there are ten, it is starting to get ugly.\n\nI ended up moving all the transformation definitions into a `zsh` hash and I created a little helper function to add new definitions to that hash. When you call [zsh-dwim](https://github.com/oknowton/zsh-dwim), it loops over that hash testing for relevant transformations. This means we can now add transformations anywhere in our shell configuration.\n\nAdding a transformation looks like this now:\n\n _dwim_add_transform '^mkdir ' \\\n 'BUFFER=\$(echo \$BUFFER | sed -re \"s/^mkdir /cd /\")'\n\n## What's coming down the road?\n\nThere's still a lot of repetitive nonsense to eliminate. I need to factor out all those \"BUFFER=\$(echo \$BUFFER | ... )\" bits. They're repeated in every single transformation.\n\nI'd also like to make use of more data in deciding which transformation to run. For instance, it might only make sense to call `ssh-keygen` if the `ssh` command fails. \n\nThe [zsh-dwim](https://github.com/oknowton/zsh-dwim) repository is ready to be pulled into [Prezto](https://github.com/sorin-ionescu/prezto) as a `git` submodule. It can probably be used as a plugin with [oh-my-zsh](https://github.com/robbyrussell/oh-my-zsh) pretty easily, and the `init.zsh` file can probably be `source`d right into plain old `zsh` without, hopefully, any problem at all.