v0.1.6

• core::to_kmers and core::encode now have ambiguity policy. The old behaviour implemented in the core::no_ambiguity_policy
• Implemented core::one_ambiguity_policy which allows one ambiguous base pair per k-mer
• With the core::one_ambiguity policy enabled, core::to_kmers now returns another type
• Added rappas::io::clean_sequence to filter gaps in the sequence (requires copying of the input string)
• core::score_threshold is not log10 anymore
• Updated examples