Update documentation for crc32c, cpu

pkgs/cpu/Makefile

@@ -0,0 +1,11 @@
+all: build test
+.PHONY: all
+
+build:
+	@godep go build
+
+test: build
+	@godep go test -race -coverprofile=cover.out
+
+clean:
+	@rm -v cover.out

pkgs/cpu/doc.go

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+// Package cpu provides wrapper around assembly functions for checking processor
+// instruction capabilities for SSE4.1, AVX, AVX2 support
+//
+// Example
+//
+// ``cpu.HasSSE41()`` returns true for SSE4.1 instruction support, false otherwise
+//
+// ``cpu.HasAVX()`` returns true for AVX instruction support, false otherwise
+//
+// ``cpu.HasAVX2()`` returns true for AVX2 instruction support, false otherwise
+package cpu