travis: run ci on all branches
travis: run ci on all branches

Was playing with a few items for rust-embedded-bot support
but this item is not necessary and prevents travis from
running tests on branches other than 'auto'.

Signed-off-by: Paul Osborne <b6afffd6c1a00645fdd04b09edf63d034a949a39@gmail.com>

rust-embedded/rust-sysfs-gpio,marjakm/rust-sysfs-gpio,nastevens/rust-sysfs-gpio