fprof: document Cachegrind support
fprof: document Cachegrind support

choptastic/rebar,bsmr-erlang/rebar,K2InformaticsGmbH/rebar,K2InformaticsGmbH/rebar,oubiwann/rebar,jacktang/rebar,rebar/rebar,apache/couchdb-rebar,jacktang/rebar,rebar/rebar,bsmr-erlang/rebar,apache/couchdb-rebar,matwey/rebar,lrascao/rebar,oubiwann/rebar,K2InformaticsGmbH/rebar,paulo-ferraz-oliveira/rebar,lrascao/rebar,matwey/rebar,lrascao/rebar,paulo-ferraz-oliveira/rebar,jacktang/rebar,rebar/rebar,lrascao/rebar,norton/rebar,norton/rebar,choptastic/rebar,matwey/rebar,matwey/rebar,choptastic/rebar,K2InformaticsGmbH/rebar,apache/couchdb-rebar,norton/rebar,bsmr-erlang/rebar,oubiwann/rebar,lrascao/rebar,K2InformaticsGmbH/rebar,bsmr-erlang/rebar,norton/rebar,paulo-ferraz-oliveira/rebar,matwey/rebar