add valid gem for validation

Gemfile.lock

@@ -6,6 +6,7 @@ PATH
       faraday_middleware (~> 0.9.0)
       nokogiri (~> 1.6, >= 1.6.6)
       typhoeus (~> 0.7.0)
+      valid (~> 0.5.0)
     diaspora_federation-rails (0.0.3)
       diaspora_federation (= 0.0.3)
       rails (~> 4.2)
@@ -238,6 +239,7 @@ GEM
       thread_safe (~> 0.1)
     uuid (2.3.8)
       macaddr (~> 1.0)
+    valid (0.5.0)
     webmock (1.21.0)
       addressable (>= 2.3.6)
       crack (>= 0.3.2)

diaspora_federation.gemspec

@@ -24,4 +24,5 @@ Gem::Specification.new do |s|
   s.add_dependency "faraday", "~> 0.9.0"
   s.add_dependency "faraday_middleware", "~> 0.9.0"
   s.add_dependency "typhoeus", "~> 0.7.0"
+  s.add_dependency "valid", "~> 0.5.0"
 end