Remove old rubies from all_tests
Land #57, documentation change
Update spec files to make them run with ruby 1.9.3p484, 2.0.0p457 and 2.1.2p95
and with rspec 3.0.0.
Correct some bugs on IPv6 length calculation.

* Packet#recalc now call ipv6_recalc with arg equals to :all or :ipv6.
* IPv6Header#ipv6_recalc now calls itself with arg=:ipv6_len (instead of
  :len) when called with arg=:all.
Update packetfu.gemspec: rspec must be >= 2.14.1.
Add rspec-its as development dependency in gemspec.
Merge pull request #66 from sdaubert/ruby21

Update spec files to make them run with rspec 3.0.0 and ruby >= 1.9.3
Merge branch 'master' into ipv6
Merge pull request #67 from sdaubert/ipv6

Correct some bugs on IPv6 length calculation.