Update connections notation in tutorials

[mstechly]

Given the completion of PsiQ/qref#113, once new QREF version is released (i.e. higher than 0.6.2), we can update Bartiq to make use of the new, more concise way of defining connections.

Instead of:

connections = [{"source": "a.out", "target": "b.in"}]

we can now do:

connections = ["a.out -> b.in"]

Which should make examples slightly more pleasant to work with :)