Vcf::Header: move op<< back into vcf ns for ADL
add reversed() helper for streamJoin()
update ycm config to find gtest
Vcf::MultiWriter

Constructed with a list of file paths, this guy accepts entries and
routes them to the correct output file by matching up the sourceIndex in
their header with the list of paths.
empty test for VcfGenotypeMatcher
vcf-compare: fix output format, refactoring

now the output is more like vcf-compare-gt