Please fix composer file to load with 5.6.x

[roblesterjr04]

I can't load on 5.6.x
Here is the issue:

Problem 1
- Can only install one of: laravel/framework[v5.6.9, 5.5.x-dev].
- Can only install one of: laravel/framework[5.5.x-dev, v5.6.9].
- Can only install one of: laravel/framework[5.5.x-dev, v5.6.9].
- laravel-frontend-presets/bootstrap-4 0.9.4 requires laravel/framework 5.5.* -> satisfiable by laravel/framework[5.5.x-dev].
- Installation request for laravel-frontend-presets/bootstrap-4 ^0.9.4 -> satisfiable by laravel-frontend-presets/bootstrap-4[0.9.4].
- Installation request for laravel/framework (locked at v5.6.9, required as 5.6.*) -> satisfiable by laravel/framework[v5.6.9].

[amadeann]

5.6 includes Bootstrap 4 by default.