Monkeypatch to pass array params without an index

typhoeus/typhoeus#320

We were seeing array params tranformed into the following:
/event?groups[0]=open-forum&groups[1]=armory-films

but we need the client to send array params to various API
services in the following (valid) format:
/event?groups[]=open-forum&groups[]=armory-films

lib/ethon/easy/queryable.rb

@@ -94,7 +94,7 @@ def recursively_generate_pairs(h, prefix, pairs)
           end
         when Array
           h.each_with_index do |v, i|
-            key = "#{prefix}[#{i}]"
+            key = "#{prefix}[]"
             pairs_for(v, key, pairs)
           end
         end

spec/ethon/easy/queryable_spec.rb

@@ -108,8 +108,8 @@
 
       it "transforms" do
         expect(pairs).to include([:a, 1])
-        expect(pairs).to include(["b[0]", 2])
-        expect(pairs).to include(["b[1]", 3])
+        expect(pairs).to include(["b[]", 2])
+        expect(pairs).to include(["b[]", 3])
       end
     end
 
@@ -118,15 +118,15 @@
         let(:hash) { {:a => {:b => ["hello", "world"]}} }
 
         it "transforms" do
-          expect(pairs).to eq([["a[b][0]", "hello"], ["a[b][1]", "world"]])
+          expect(pairs).to eq([["a[b][]", "hello"], ["a[b][]", "world"]])
         end
       end
 
       context "when hash" do
         let(:hash) { {:a => {:b => [{:c =>1}, {:d => 2}]}} }
 
         it "transforms" do
-          expect(pairs).to eq([["a[b][0][c]", 1], ["a[b][1][d]", 2]])
+          expect(pairs).to eq([["a[b][][c]", 1], ["a[b][][d]", 2]])
         end
       end
 
@@ -136,7 +136,7 @@
         let(:hash) { {:a => {:b => [file]}} }
 
         it "transforms" do
-          expect(pairs).to eq([["a[b][0]", file_info]])
+          expect(pairs).to eq([["a[b][]", file_info]])
         end
       end
     end