make it possible to push lists as paramters

This makes it possible to push lists as paramters by naming the
variables with `[]` at the end, for example `foo[]`.

lib/zero/request/parameter.rb

@@ -21,6 +21,8 @@ module Zero
         'application/x-www-form-urlencoded',
         'multipart/form-data'
       ].to_set
+      # match keys for list attribute
+      REGEX_MATCH_LIST = /\[\]$/
 
       # get the query parameters
       attr_reader :query
@@ -95,7 +97,16 @@ module Zero
       # @param query [String] the query string
       # @return [Hash] the key/valuie pairs
       def parse_string(query)
-        Hash[URI.decode_www_form(query)]
+        result = {}
+        URI.decode_www_form(query).each do |p|
+          if p.first.match(REGEX_MATCH_LIST)
+            result[p.first] ||= []
+            result[p.first] << p.last
+          else
+            result[p.first] = p.last
+          end
+        end
+        result
       end
     end
   end

spec/unit/zero/request/parameter/payload_spec.rb

@@ -31,6 +31,25 @@ describe Zero::Request::Parameter, '#payload' do
     its(:payload) { should == {'bar' => 'foo bar'} }
   end
 
+  context 'with multiple parameters' do
+    let(:env) do
+      EnvGenerator.post('/foo', {
+        :input => 'bar=foo&foo=bar', 'CONTENT_TYPE' => 'multipart/form-data'
+      })
+    end
+    its(:payload) { should == {'foo' => 'bar', 'bar' => 'foo'} }
+  end
+
+  context 'with a list' do
+    let(:env) do
+      EnvGenerator.post('/foo', {
+        :input => 'bar[]=foo&bar[]=bar',
+        'CONTENT_TYPE' => 'multipart/form-data'
+      })
+    end
+    its(:payload) { should == {'bar[]' => ['foo', 'bar']} }
+  end
+
   # TODO behaves like this, but is this really good like this?
   context 'with a post body and content type application/json' do
     let(:env) do