Core styles imported

First draft
Fixing some scss problems
adding dzslides to the sass path
Changing the name to dzslides-core

I may decide to include some transitions and maybe some themes
eventually, so I want to make sure that we have the proper naming scheme
in place already.
Updating the README, and dependencies

I know we work with the latest (at time of writing 3.3.7) sass, and also
all the way back to 3.2.
Merge branch 'feature/sass-integration' into develop