Performance Bottlenecks

[pranavtbhat]

• [x] seteprop! is slow because edge listing is slow. Make edgeiter an AbstractArray?
• [x] fadj creates a new array in SparseMatrixAM. Try copy! on a preallocated array?
• [x] Replace all instances of Map with list comprehensions
• [x] Port to 0.5 asap, for function type inference
• [x] Rewrite the labelling module for 0.5