add autoredirect support

Fixes issue #10

Example:

    2.0.0-p247 :013 > a = Ipgeobase.lookup "46.8.114.116"
    Fatal error: Space required after the Public Identifier at :1.
    Fatal error: SystemLiteral " or ' expected at :1.
    Fatal error: SYSTEM or PUBLIC, the URI is missing at :1.
    LibXML::XML::Error: Fatal error: SYSTEM or PUBLIC, the URI is missing at :1.
    	from /home/vagrant/.rvm/gems/ruby-2.0.0-p247/gems/happymapper-0.4.1/lib/happymapper.rb:91:in `parse'
    	from /home/vagrant/.rvm/gems/ruby-2.0.0-p247/gems/happymapper-0.4.1/lib/happymapper.rb:91:in `parse'
	from /home/vagrant/.rvm/gems/ruby-2.0.0-p247/gems/ipgeobase-0.1.0/lib/ipgeobase.rb:12:in `lookup'
	from (irb):13
	from /home/vagrant/.rvm/rubies/ruby-2.0.0-p247/bin/irb:16:in `<main>' 

    2.0.0-p247 :014 > a = Ipgeobase.lookup "46.8.114.116"
     => #<Ipgeobase::IpMetaData:0x000000027f3dc8 @inetnum="46.8.112.0 - 46.8.127.255", @city="Ульяновск", @country="RU", @region="Ульяновская область", @district="Приволжский федеральный округ", @lat=54.32148, @lng=48.385651>

This was due to wrong response from server. It's try redirect you.