Add OSX install script (#1947)

* Add OSX install script

* Address PR comments

scripts/install/install_tendermint_osx.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+
+# XXX: this script is intended to be run from
+# an MacOS machine
+
+# as written, this script will install
+# tendermint core from master branch
+REPO=github.com/tendermint/tendermint
+
+# change this to a specific release or branch
+BRANCH=master
+
+if ! [ -x "$(command -v brew)" ]; then
+  echo 'Error: brew is not installed, to install brew' >&2
+  echo 'follow the instructions here: https://docs.brew.sh/Installation' >&2
+  exit 1
+fi
+
+if ! [ -x "$(command -v go)" ]; then
+  echo 'Error: go is not installed, to install go follow' >&2
+  echo 'the instructions here: https://golang.org/doc/install#tarball' >&2
+  echo 'ALSO MAKE SURE TO SETUP YOUR $GOPATH and $GOBIN in your ~/.profile: https://github.com/golang/go/wiki/SettingGOPATH' >&2
+  exit 1
+fi
+
+if ! [ -x "$(command -v make)" ]; then
+  echo 'Make not installed, installing using brew...'
+  brew install make
+fi
+
+# get the code and move into repo
+go get $REPO
+cd $GOPATH/src/$REPO
+
+# build & install
+git checkout $BRANCH
+# XXX: uncomment if branch isn't master
+# git fetch origin $BRANCH
+make get_tools
+make get_vendor_deps
+make install