add pull requests missing from 0.18.0 release to CHANGES.md, fixes #867
add pull requests missing from 0.18.0 release to CHANGES.md, fixes #867

heuermh/adam,erictu/adam,tdanford/adam,erictu/adam,laserson/adam,rnpandya/adam,heuermh/adam,rnpandya/adam,laserson/adam,bigdatagenomics/adam,massie/adam,laserson/adam,tdanford/adam,massie/adam,bigdatagenomics/adam,laserson/adam,erictu/adam,heuermh/adam,tdanford/adam,bigdatagenomics/adam,rnpandya/adam,massie/adam,erictu/adam,tdanford/adam,rnpandya/adam,bigdatagenomics/adam,massie/adam,heuermh/adam