Added copyright header and ran golint

graphs/initializer.go

graphs/permute.go

graphs/permute_test.go

graphs/precomputation/decrypt.go

graphs/precomputation/decrypt_test.go

graphs/precomputation/permute.go

graphs/precomputation/permute_test.go

graphs/precomputation/reveal.go

graphs/precomputation/reveal_test.go

graphs/precomputation/share.go

graphs/precomputation/share_test.go

graphs/precomputation/strip.go

graphs/precomputation/strip_test.go