filter out hidden files, too, like .DS_Store on OSX

[CamDavidsonPilon]

I hit a problem where the customize script was trying to execute a local .DS_Store on my Mac. More generally, users probably don't want hidden files and directories to be executed.

Before

> find workspace/scripts -maxdepth 1 -not -type d
workspace/scripts/11-add-firstboot
workspace/scripts/.DS_Store
workspace/scripts/07-install-logging
workspace/scripts/06-install-pioreactor
workspace/scripts/99-finish
workspace/scripts/12-add-pioreactor-bash-scripts
workspace/scripts/09-install-mosquitto
workspace/scripts/04-install-services
workspace/scripts/08-install-ui
workspace/scripts/01-install-python-and-git
workspace/scripts/10-install-db
workspace/scripts/03-configure-rpi
workspace/scripts/05-install-i2c

After

> find workspace/scripts -maxdepth 1 -not -type d -not -path '*/\.*'
workspace/scripts/11-add-firstboot
workspace/scripts/07-install-logging
workspace/scripts/06-install-pioreactor
workspace/scripts/99-finish
workspace/scripts/12-add-pioreactor-bash-scripts
workspace/scripts/09-install-mosquitto
workspace/scripts/04-install-services
workspace/scripts/08-install-ui
workspace/scripts/01-install-python-and-git
workspace/scripts/10-install-db
workspace/scripts/03-configure-rpi
workspace/scripts/05-install-i2c

[foosel]

Good point, thank you!