Add a "request_raw" function.

It does not alter the body of request and response. While "request"
function always decode response body as JSON and turned it into a
HashRef.

In the scenario of doing bulk-processing (testing/analytic),
this allows us to simply store the raw JSON text and parse them
in bulk latter.
Merge branch 'master' of github.com:gugod/Elastijk

Conflicts:
	lib/Elastijk.pm