Add yara to ubuntu-precise; resolves travis-ci/apt-package-whitelist#2474
Add yara to ubuntu-precise; resolves travis-ci/apt-package-whitelist#2474

Packages: yara libyara3 libyara-dev python-yara python3-yara yara-doc yara-dbg

travis-ci/apt-package-whitelist,travis-ci/apt-package-whitelist