Add super basic support for loading a non-default template

[cowboy]

This would probably help a lot. Maybe allow something like this:

grunt-init /path/to/tasks/init/custom-template.js

To do what this does:

grunt-init --tasks /path/to/tasks custom-template

Which is to support a custom init template.

[tkellen]

Are we still supporting loading from ~/tasks ?

[cowboy]

Init templates can still be placed in ~/.grunt/tasks/init/. And an init template can be specified on the command line to grunt-init like grunt-init --tasks /path/to/tasks custom-template. It's just a bit awkward.

[cowboy]

This was added in 7460e9a and will be supported when that branch is merged.