Switch links over to jmespath.org
Switch links over to jmespath.org

The readthedocs links are for the python implementation of
jmespath, and now that there's a jmespath.org, I'm eventually
going to remove the readthedocslink for the specification and just
link to jmespath.org/specification.html.  There's already a
deprecation warning on the readthedocs link.

I also added a link to the jmespath tutorial. The previous link
to JMESPath examples was linking to the first examples in the spec,
which was just the examples for the first section, identifiers.

burtcorp/burtpath,sferik/jmespath.rb,jmespath/jmespath.rb,burtcorp/burtpath,effata/jmespath.rb