fix: add missed definition for Slaver::Proxy#respond_to_missing?

Slaver::Proxy#respond_to? now will check if Slaver::Proxy#safe_connection
could respond to specified method.

lib/slaver/proxy.rb

@@ -34,5 +34,9 @@ def safe_connection
     def method_missing(method, *args, &block)
       safe_connection.send(method, *args, &block)
     end
+
+    def respond_to_missing?(method, include_private = false)
+      safe_connection.respond_to?(method, include_private) || super
+    end
   end
 end

spec/lib/slaver/proxy_spec.rb

@@ -0,0 +1,27 @@
+require 'spec_helper'
+
+describe Slaver::Proxy do
+  describe 'connection methods delegation' do
+    context 'when proxy connection does not respond to called method' do
+      it 'does not respond and raises NameError' do
+        expect(Foo.on(:other).connection.respond_to?(:not_existed_method)).to eq(false)
+        expect { Foo.on(:other).connection.method(:not_existed_method) }.to raise_error(NameError)
+        expect { Foo.on(:other).connection.not_existed_method }.to raise_error(NameError)
+      end
+    end
+
+    context 'when proxy connection responds to called method' do
+      let(:query) { "SELECT COUNT(*) FROM #{Foo.quoted_table_name} WHERE name = 'other_1'" }
+
+      it 'responds to method by calling it on proxy connection' do
+        Foo.on(:other).create!(name: 'other_1')
+        Foo.on(:other).create!(name: 'other_2')
+
+        expect(Foo.on(:other).connection.respond_to?(:select_value)).to eq(true)
+        expect(Foo.on(:other).connection.method(:select_value)).to be
+        expect(Foo.on(:other).connection.select_value(query).to_i).to eq(1)
+        expect(Foo.connection.select_value(query).to_i).to eq(0)
+      end
+    end
+  end
+end