feat!: base specific hop parameters in homopoly-pair-hmm

[tedil]

build_transition_table now expects something that implements the trait BaseSpecificHopParameters instead of HopParameters, since the latter can be expressed as the first (i.e. there's a default impl of BaseSpecificHopParameters for anything that implements HopParameters which just uses the base-agnostic homopolymer run start / extend probabilities)

[coveralls]

Coverage decreased (-0.01%) to 88.764% when pulling 1b09989 on tedil:base-specific-hphmm into 8a900a2 on rust-bio:master.