update bcrypt gem

Author: ivailop

Gemfile.lock

@@ -31,7 +31,7 @@ GEM
       public_suffix (>= 2.0.2, < 4.0)
     arel (5.0.1.20140414130214)
     ast (2.3.0)
-    bcrypt (3.1.11)
+    bcrypt (3.1.18)
     bootstrap-sass (3.1.1.1)
       sass (~> 3.2)
     brakeman (3.7.2)