Fix NullPointerException when equals or hashCode are called on proxy instance

They look something like this:

java.lang.NullPointerException
	at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:88)
	at feign.$Proxy16.equals(Unknown Source)

In  my particular instance, I had a proxy created by Feign registered in a Spring application context,
and it resulted in a NullPointerException on application shutdown.
Merge pull request #61 from davidmc24/fix-equals-hashcode

Fix NullPointerException when equals or hashCode are called on proxy instance
issue #53: update readme with a warning
Remove support for Observable methods.
Merge pull request #62 from Netflix/no-observable

Remove support for Observable methods.
SaxDecoder now decodes multiple types.
Remove pattern decoders in favor of SaxDecoder.
Merge pull request #63 from Netflix/global-saxdecoder

global custom XML decoder