make siacrypto/random smaller and faster
simplify buildProof using SectionReader
reimplement MerkleCollapse recursively
switch back to ReadSeeker in buildProof

...plus various other touchups
cleanup erasure and improve error handling
reformat addresses as {host port id}
better comments in network package
add comments to siaencoding package
rename CalculateHash -> HashBytes
change signature of RandomInt
remove 'unsafe' import from signatures.go
add tests and benchmarks to hash_test.go
stylistic changes to siacrypto package
change k and m to ints
add benchmarks to signatures_test.go
add benchmark to encoding_test.go
add benchmark to rpcnetwork_test.go
make RegisterHandler return an Address
remove last 'math' import
add comments/style changes to consensus package