Make /install/client.html redirect to /using/install-client.html
Make /install/client.html redirect to /using/install-client.html

Because old clients reference the former page, which is now a broken
link on ReadTheDocs

Fixes: GH-921

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