Merge pull request #36 from toxeus/develop

git: improve pre-push hook error message
install_sample_data.sh: Point to upstream repo
Merge pull request #37 from lclc/updateSampleScriptData

install_sample_data.sh: Point to upstream repo
git hook: also check for clang-format-3.5

On Ubuntu systems the binary is called clang-format-3.5.