[Gemfile] Remove rbnacl-libsodium, because it's very long to build and not actually necessary

Gemfile

@@ -6,7 +6,6 @@ gem "diffy"
 gem "mediawiki_api"
 gem "net-ssh"
 gem "rbnacl", "~> 3.2", "< 5.0"
-gem "rbnacl-libsodium"
 gem "bcrypt_pbkdf", "~> 1.0"
 gem "dns-zone"
 gem "ruby-cute", :require => "cute"

Gemfile.lock

@@ -106,8 +106,6 @@ GEM
     rb-readline (0.5.5)
     rbnacl (3.4.0)
       ffi
-    rbnacl-libsodium (1.0.15.1)
-      rbnacl (>= 3.0.1)
     regexp_parser (1.6.0)
     rest-client (1.8.0)
       http-cookie (>= 1.0.2, < 2.0)
@@ -200,7 +198,6 @@ DEPENDENCIES
   net-ssh
   peach
   rbnacl (~> 3.2, < 5.0)
-  rbnacl-libsodium
   restfully
   rspec
   ruby-cute