Could you specify the required go version in README?

[freewind]

I run make all after cloning ontology source code, and it reports such error:

make all
go build  -ldflags "-X github.com/ontio/ontology/common/config.Version=v1.0.1"  -o ontology main.go
http/restful/restful/router.go:22:2: cannot find package "context" in any of:
	/root/go/src/github.com/ontio/ontology/vendor/context (vendor tree)
	/usr/lib/go-1.6/src/context (from $GOROOT)
	/root/go/src/context (from $GOPATH)
vendor/golang.org/x/crypto/ripemd160/ripemd160block.go:12:2: cannot find package "math/bits" in any of:
	/root/go/src/github.com/ontio/ontology/vendor/math/bits (vendor tree)
	/usr/lib/go-1.6/src/math/bits (from $GOROOT)
	/root/go/src/math/bits (from $GOPATH)
Makefile:20: recipe for target 'ontology' failed
make: *** [ontology] Error 1

and I found the go version on my ubuntu server is:

$ go version
go version go1.6.2 linux/amd64

looks a little old, but which is the latest version installed by sudo apt-get install golang-go.

Finally, I upgrade go to v1.10 (https://github.com/golang/go/wiki/Ubuntu), it works.

go version go1.10 linux/amd64

I think we could specify the required go version in README

[freewind]

I found it already in README, sorry