Add styles to watched directories for watch task

Fixes #80 

## Problem
`buildStyles` is not being watched, so changing a `.sass` or `.scss` file in `buildStyles` will not trigger a rebuild.

## Solution
Add the path.

## Testing
- Create a `.scss` or `.sass` file in a `sass` directory (the default path setting for `buildStyles`
- Start a `gulp watch`
- Edit the sass file, ensure there is a rebuild triggered upon save

@trentgrover-wf 
@evanweible-wf 
FYI
@brentechols-wf