travis: use scan.coverity.com addon
coverity scan: fix some warnings

Mostly uninitialized variables.
coverity scan: don't build if coverity is on
pyTuttle: remove some comments
build fix for clang
travis: add osx
Merge pull request #349 from tuttleofx/coverity_scan

Coverity scan
Merge pull request #335 from fabiencastan/travis_multi_os

travis: add osx
fix for compilers compatibility
coverity_scan: don't build binding
coverity_scan: add exclude for travis build matrix
fix cppcheck warning: use reference
fix cppcheck warning: explicit parentheses
fix cppcheck warning: missing variables in operator=
fix cppcheck warning: operator= signature
Params: bug fix, initialization with default value
fix cppcheck warning: remove unused var
Crop: bug fix in changed param updates
Crop: crop by default in the crop node
travis: don't reinstall packages