Load JSON-LD contexts from URL using input stream method of JSONFactory

Avoids problems with content type which breaks URL.getContent() - 
instead we make a URLConnection with the appropriate Accept headers. 

Note that this assumes UTF-8 encoding which is required by JSON
specification of application/json (and thus for application/ld+json)
Tidy..
Test request property using fake URLStreamHandler
Swapped order so application/ld+json is first
Merge remote-tracking branch 'upstream/master'
Merge branch 'from-url'
Merge branch 'from-url'
Merge remote-tracking branch 'upstream/master'
Merge branch 'uri-accept-headers'
Merge remote-tracking branch 'upstream/master'
Network-dependent integration tests using failsafe
Test cache is used even across redirects
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
jena dependency bumped to 2.10.1
Merge remote-tracking branch 'upstream/master'

Conflicts:
	pom.xml
Make our master match upstream/master
 Avoid testing anonymous bnodes literally - check using Jena model
Test each statement separately
Merge branch 'master' of github.com:stain/jsonld-java into fred23