Add reference sequence index cache to speed up query by 20% for certain
usecases
Merge pull request #23 from samtools/bw_skipToSequenceOptimization

Add reference sequence index cache to speed up query by 20% for certain
IntervalTreeMap added two method to test interval overlapping
Merge pull request #24 from samtools/pl_intervaltreemap

IntervalTreeMap added two method to test interval overlapping