Adding Tumblr example.
Adding Tumblr example.

Should look into streamlining these examples, everything is repeated except for the service that's being initialized.

Signed-off-by: Ben Corlett <9fc0b04505a02c47a9e61f970105683228d674a6@me.com>

thephpleague/oauth1-client,Gelembjuk/oauth1-client,stevenmaguire/oauth1-client