router/testing: rename Instance to FakeRouter
router/testing: rename Instance to FakeRouter

Now that the type is unexported, we can export the variable.

guilhermebr/tsuru,guilhermebr/tsuru,jblancett/tsuru,cgvarela/tsuru,cezarsa/tsuru,gwmoura/tsuru,mderaldo/tsuru,hugoantunes/tsuru,RichardKnop/tsuru,RichardKnop/tsuru,Endika/tsuru,tsuru/tsuru,jblancett/tsuru,guilhermebr/tsuru,mderaldo/tsuru,tsuru/tsuru,4eek/tsuru,ggarnier/tsuru,ggarnier/tsuru,hcxiong/tsuru,cezarsa/tsuru,gciotta/tsuru,tuxmonteiro/tsuru,cgvarela/tsuru,cezarsa/tsuru,RichardKnop/tsuru,Endika/tsuru,hcxiong/tsuru,Endika/tsuru,jblancett/tsuru,cgvarela/tsuru,gwmoura/tsuru,kgrvamsi/tsuru,tsuru/tsuru,gciotta/tsuru,ArxdSilva/tsuru,hugoantunes/tsuru,gwmoura/tsuru,firebitsbr/tsuru,gciotta/tsuru,guilhermebr/tsuru,ArxdSilva/tsuru,ggarnier/tsuru,kgrvamsi/tsuru,4eek/tsuru,4eek/tsuru,tuxmonteiro/tsuru,ArxdSilva/tsuru,firebitsbr/tsuru,tuxmonteiro/tsuru,tsuru/tsuru,ArxdSilva/tsuru,firebitsbr/tsuru,mderaldo/tsuru,hcxiong/tsuru,kgrvamsi/tsuru,cezarsa/tsuru,ggarnier/tsuru