Document the instruction how to build on mac about grv HOT 7 CLOSED

ή brew info readline
readline: stable 7.0.3 (bottled) [keg-only]
Library for command-line editing
https://tiswww.case.edu/php/chet/readline/rltop.html
/usr/local/Cellar/readline/7.0.3_1 (46 files, 1.5MB)
  Poured from bottle on 2017-05-23 at 16:48:22
From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/readline.rb
==> Caveats
This formula is keg-only, which means it was not symlinked into /usr/local,
because macOS provides the BSD libedit library, which shadows libreadline.
In order to prevent conflicts when programs look for libreadline we are
defaulting this GNU Readline installation to keg-only..

For compilers to find this software you may need to set:
    LDFLAGS:  -L/usr/local/opt/readline/lib
    CPPFLAGS: -I/usr/local/opt/readline/include

$ go version
go version go1.9.4 darwin/amd64

$ git show
commit ffbd489206c5e76b5c2e7ac251f088880678ea06 (HEAD -> master, tag: v0.1.2, origin/master, origin/HEAD)
Author: Richard Burke <[email protected]>
Date:   Wed Feb 7 20:15:05 2018 +0000

$ make
[...]
go build github.com/rgburke/grv/cmd/grv/vendor/gopkg.in/libgit2/git2go.v25: invalid pkg-config package name: --static
make[1]: *** [install-static] Error 1
make: *** [build-libgit2] Error 2

$ go build --tags static -ldflags "-X 'main.version=v0.1.2-0-gffbd489' -X 'main.headOid=ffbd489' -X 'main.buildDateTime=2018-02-07 13:37:56 PST'" -o grv ./cmd/grv
go build github.com/rgburke/grv/cmd/grv/vendor/gopkg.in/libgit2/git2go.v25: invalid pkg-config package name: --static