* Include formatting check to the `make check` rule
... and give it its own standalone target too (make fmt-check)
Show diff on fmt-check failure
Do not allow running "fmt-check" with incompatible go version
Also simplify the `fmt` rule
* Forbid running "make fmt" with Go version != 1.7 or 1.8
* Ignore bindata.go for spelling and formatting checks
also remove duplicated variable assignment for GOFILES
* Run `make fmt`
f6b58964d7