Make build and install scripts more portable (#325)

scripts/build.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 version=$(git describe --exact-match --tags 2>/dev/null || git describe 2>/dev/null || echo "prerelease")
 go build \

scripts/install.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 set -e