Add function to get user from roster by their nick
Add function to get user from roster by their nick

Useful for plugins that expect a user mention in hear() or
respond_to()

chillipeper/will,mvanbaak/will,dmuntean/will,jacobbridges/will,mike-love/will,skoczen/will,fredsmith/will,shadow7412/will,mvanbaak/will,skoczen/will,brandonsturgeon/will,Ironykins/will,mike-love/will,jacobbridges/will,ammartins/will,ammartins/will,wontonst/will,shadow7412/will,dmuntean/will,wontonst/will,Regner/will,pcurry/will,dmuntean/will,pcurry/will,fredsmith/will,shadow7412/will,Ironykins/will,woohgit/will,skoczen/will,grahamhayes/will,wontonst/will,brandonsturgeon/will,fredsmith/will,ammartins/will,mvanbaak/will,grahamhayes/will,mike-love/will,woohgit/will,woohgit/will,brandonsturgeon/will,chillipeper/will,jacobbridges/will,Regner/will,pcurry/will,grahamhayes/will,chillipeper/will,Ironykins/will,Regner/will