Sage 8.1.0

• Move HTML5 Boilerplate's Google Analytics snippet to Soil (#1382)
• Run gulp build if bower.json is changed (#1378)
• Remove namespace from base.php (#1372)
• Allow build directory to be customized (#1352, #1366)
• Update ConditionalTagCheck and usage docs (#1365)
• Change default gallery columns to 3 (#1364)
• Apply script_loader_src filter to jQuery fallback (#1363)