jtnystrom/Discount: Version 2.0.0

This version includes the following improvements.

• Nearly 50% faster counting due to better algorithms, including a version of radix sort from the Fastutil library
• Automatic selection of the most appropriate minimizer set from a directory, by matching with the desired (k, m) values
• Support for interactive notebooks (a Zeppelin example is included) and a restructured API to support this
• Hashed superkmers can now be queried by sequences to find matching k-mers
• Support for lowercase nucleotide letters in input
• Support for user-defined minimizer orderings (-o given)
• Various simplifications and enhancements