Update high_voltage

Author: jurre

Gemfile.lock

@@ -682,7 +682,7 @@ GEM
  html2haml (>= 1.0.1)
  railties (>= 4.0.1)
  hashtel (0.0.2)
- high_voltage (2.2.0)
+ high_voltage (3.1.2)
  holidays (1.2.0)
  html2haml (2.2.0)
  erubis (~> 2.7.0)