add travis-ci support to maintenance branch

since it insists on watching
add explicit assignment ops for certain classes

gcc 4.4 requires us to explicitly declare our own move constructors :(
this means we have to make explicit assignment operators also

Fixes #2
updates for clang compatibility
fix lazy sample data parsing for vcf entry output

printing an entry was always forcing all sample data to be parsed.
Merge branch 'maintenance-v1.6' into maintenance-v1.7

bugfix for vcf output performance (lazy sample parsing)