Compatibility fix of URI#hostname and URI#hostname=

These methods works differently with URI#host and URI#host= for IPv6
address.  Introduce method definitions from stdlib uri module for
compatibility.

Assigning bare IPv6 address via URI#host= should raise an exception but
this commit just adds a pending spec for compatibility concern.  Can we
raise an exception as well as stdlib uri module?
Merge pull request #115 from therabidbanana/master

IDNA Pure Fix and README update
Updating version, CHANGELOG, and gemspec. Closes #116.
Merge branch 'master' of github.com:sporkmonger/addressable
Make it easier to subclass Addressable::URI
Add tests for subclassing behavior
Merge pull request #118 from Thibaut/master

Make it easier to subclass Addressable::URI
Merge pull request #119 from therabidbanana/master

Allow Symbols for Partial Expansion
Now checks scheme to ensure IP-based before complaining about missing hierarchical part. Fixes #120.
Merge branch 'master' of github.com:sporkmonger/addressable
Updated copyright date to 2013.

Conflicts:
	spec/addressable/specializations/mailto_spec.rb
Added #empty? method.
Updating CHANGELOG with information about changes from 7256b76.
Merge pull request #89 from nahi/ipv6_host

Compatibility fix of URI#hostname and URI#hostname=
Fixed type checking and documentation from #89.
Added changes from #89 to CHANGELOG.
Updated copyright date to 2013.
Adding gem version badge and coveralls.
Merge branch 'master' of github.com:sporkmonger/addressable
Apparently the tests break Coveralls. Heh.