Version 1.3.1

Maintenance & bugfix release, with some notable enhancements. Details below.

Maintenance
Updated SB Admin 2 theme to latest release (3.3.7).
Added Gulp support for better dependency organization.
Dependencies updated to latest versions, now accurately reflected in the project graph.
Replaced bower_components with a vendor directory in project root, containing only the distribution versions. Substantially reduced the number of installed files. See #171. Addresses #79.
Paves the way for eventual Bootstrap 4 compatibility.

Enhancements
Added ability to select wireless interface for WiFi client. Added ability to enable/disable visible services in the dashboard (thanks @emmanuelgeoffray).
Added support for 5GHz channels. Priority now preserved in wpa_supplicant.conf (thanks @rmarshall31).

Bugfixes
Fixes to default_configuration in the installer. Resolves #174 (thanks @Austin-RR).
Fixes to /etc/sudoers entries (thanks @jbishop129).
Patch dashboard.php to take dots in ESSID's (thanks @arduino-man).
Installs php7.0-cgi on Stretch, maintains backwards compatibility. Resolves #124.
Fixed a bug with hostapd logging scripts not moved. Resolves #138.
Fixed a permissions error with the installer. Resolves #136.