Removed lodash dependency

We weren't using lodash in our project, and while I wanted your awesome wizard directive, I'm a bit anal about layering on extra dependencies for a couple of reasons:

1. Lodash added size to our JS for a library we don't use. Something like 20-30K depending on how smart we were with using lodash's official minified build. I think you only use 3-4 functions, some of which have equivelant helpers in angular (isUndefined etc). Others of which could be reimplemented (finding a steps position in the list and finding a step by title).
2. Possibility for conflicts with other libraries that use different versions of lodash 

So I went ahead and removed lodash in my fork.

- Replaced _ helpers with angular equivelants where possible
- Reimplemented usage of `indexOf` as `stepIdx` function
- Reimplemented usages of `findWhere` with `stepByTitle`

Won't be offended if you think lodash is worth keeping around, my fork can continue to support the crowd that wants to only depend on angular.

Thanks
-Doug