hashmap: Fix the example using derived Hash + Eq
hashmap: Fix the example using derived Hash + Eq

The example derived Hash + Eq on a type that was used as *values* for
a hashmap.. for the example to make sense, we have to use a custom *key*
type.

Write a slightly more involved example, still using Vikings, but this
time as key.

I preferred using String over &str here, since that's the typical usage
and we might want to lead users down that path.

andars/rust,philyoon/rust,rprichard/rust,mihneadb/rust,ebfull/rust,zaeleus/rust,dinfuehr/rust,avdi/rust,victorvde/rust,GBGamer/rust,dwillmer/rust,mdinger/rust,l0kod/rust,vhbit/rust,bombless/rust,defuz/rust,TheNeikos/rust,miniupnp/rust,pelmers/rust,nwin/rust,KokaKiwi/rust,GBGamer/rust,hauleth/rust,AerialX/rust,XMPPwocky/rust,nwin/rust,omasanori/rust,jroesch/rust,cllns/rust,richo/rust,vhbit/rust,krzysz00/rust,pelmers/rust,untitaker/rust,zubron/rust,dwillmer/rust,nwin/rust,richo/rust,rprichard/rust,AerialX/rust-rt-minimal,aepsil0n/rust,aneeshusa/rust,rohitjoshi/rust,miniupnp/rust,mdinger/rust,mvdnes/rust,ejjeong/rust,miniupnp/rust,aneeshusa/rust,aneeshusa/rust,rprichard/rust,carols10cents/rust,rohitjoshi/rust,mahkoh/rust,avdi/rust,rohitjoshi/rust,XMPPwocky/rust,untitaker/rust,jashank/rust,mihneadb/rust,gifnksm/rust,nwin/rust,richo/rust,andars/rust,AerialX/rust-rt-minimal,rohitjoshi/rust,mvdnes/rust,philyoon/rust,kimroen/rust,zaeleus/rust,cllns/rust,mihneadb/rust,kwantam/rust,pshc/rust,l0kod/rust,jashank/rust,dwillmer/rust,graydon/rust,KokaKiwi/rust,ejjeong/rust,robertg/rust,kimroen/rust,jroesch/rust,l0kod/rust,jashank/rust,pshc/rust,andars/rust,robertg/rust,seanrivera/rust,cllns/rust,untitaker/rust,bombless/rust,bombless/rust,miniupnp/rust,untitaker/rust,AerialX/rust,reem/rust,TheNeikos/rust,gifnksm/rust,zachwick/rust,kwantam/rust,reem/rust,zachwick/rust,omasanori/rust,robertg/rust,ruud-v-a/rust,mvdnes/rust,ktossell/rust,aidancully/rust,zubron/rust,aneeshusa/rust,carols10cents/rust,zachwick/rust,miniupnp/rust,jroesch/rust,l0kod/rust,XMPPwocky/rust,l0kod/rust,aepsil0n/rust,AerialX/rust,jroesch/rust,zaeleus/rust,seanrivera/rust,carols10cents/rust,cllns/rust,ruud-v-a/rust,GBGamer/rust,zachwick/rust,philyoon/rust,pshc/rust,nwin/rust,KokaKiwi/rust,zubron/rust,rprichard/rust,kimroen/rust,graydon/rust,ruud-v-a/rust,ejjeong/rust,kimroen/rust,zachwick/rust,aidancully/rust,ejjeong/rust,AerialX/rust-rt-minimal,ktossell/rust,vhbit/rust,vhbit/rust,andars/rust,ktossell/rust,bombless/rust,avdi/rust,omasanori/rust,zubron/rust,robertg/rust,mdinger/rust,avdi/rust,zubron/rust,ktossell/rust,ebfull/rust,hauleth/rust,untitaker/rust,ejjeong/rust,vhbit/rust,nwin/rust,miniupnp/rust,GBGamer/rust,zubron/rust,robertg/rust,l0kod/rust,ruud-v-a/rust,victorvde/rust,AerialX/rust-rt-minimal,dinfuehr/rust,bombless/rust,sae-bom/rust,pshc/rust,mvdnes/rust,robertg/rust,miniupnp/rust,cllns/rust,rprichard/rust,KokaKiwi/rust,KokaKiwi/rust,reem/rust,XMPPwocky/rust,mvdnes/rust,carols10cents/rust,hauleth/rust,ebfull/rust,dinfuehr/rust,defuz/rust,omasanori/rust,zaeleus/rust,AerialX/rust,bombless/rust,dwillmer/rust,hauleth/rust,defuz/rust,pelmers/rust,rohitjoshi/rust,avdi/rust,mahkoh/rust,jroesch/rust,graydon/rust,carols10cents/rust,sae-bom/rust,defuz/rust,mihneadb/rust,nwin/rust,aepsil0n/rust,mdinger/rust,mahkoh/rust,carols10cents/rust,vhbit/rust,AerialX/rust-rt-minimal,XMPPwocky/rust,aepsil0n/rust,mvdnes/rust,zaeleus/rust,pelmers/rust,mdinger/rust,sae-bom/rust,l0kod/rust,omasanori/rust,philyoon/rust,krzysz00/rust,dinfuehr/rust,cllns/rust,andars/rust,pelmers/rust,jroesch/rust,krzysz00/rust,jashank/rust,sae-bom/rust,aidancully/rust,pshc/rust,pshc/rust,gifnksm/rust,ktossell/rust,aepsil0n/rust,aidancully/rust,mihneadb/rust,andars/rust,reem/rust,philyoon/rust,TheNeikos/rust,ktossell/rust,pshc/rust,zubron/rust,ruud-v-a/rust,AerialX/rust,avdi/rust,victorvde/rust,kwantam/rust,hauleth/rust,TheNeikos/rust,dinfuehr/rust,pelmers/rust,richo/rust,krzysz00/rust,miniupnp/rust,mahkoh/rust,sae-bom/rust,TheNeikos/rust,ejjeong/rust,ruud-v-a/rust,kwantam/rust,mahkoh/rust,krzysz00/rust,seanrivera/rust,jroesch/rust,jroesch/rust,richo/rust,untitaker/rust,reem/rust,jashank/rust,aidancully/rust,gifnksm/rust,GBGamer/rust,l0kod/rust,GBGamer/rust,dwillmer/rust,jashank/rust,dinfuehr/rust,victorvde/rust,AerialX/rust,graydon/rust,jashank/rust,gifnksm/rust,pshc/rust,krzysz00/rust,ktossell/rust,vhbit/rust,AerialX/rust-rt-minimal,rprichard/rust,zachwick/rust,XMPPwocky/rust,omasanori/rust,aepsil0n/rust,kimroen/rust,gifnksm/rust,victorvde/rust,aneeshusa/rust,seanrivera/rust,TheNeikos/rust,graydon/rust,sae-bom/rust,zaeleus/rust,mahkoh/rust,seanrivera/rust,dwillmer/rust,rohitjoshi/rust,vhbit/rust,ebfull/rust,bombless/rust-docs-chinese,defuz/rust,mdinger/rust,reem/rust,philyoon/rust,kimroen/rust,kwantam/rust,seanrivera/rust,mihneadb/rust,hauleth/rust,graydon/rust,dwillmer/rust,defuz/rust,KokaKiwi/rust,zubron/rust,GBGamer/rust,nwin/rust,ebfull/rust,jashank/rust,richo/rust,kimroen/rust,kwantam/rust,GBGamer/rust,ebfull/rust,dwillmer/rust,victorvde/rust,aneeshusa/rust,aidancully/rust