Added install script

install.sh

+#!/bin/sh
+
+if [ "$1" == "" ]; then
+	echo "Usage $0 executable branch ethereum develop"
+	echo "executable    ethereum or ethereal"
+	echo "branch        develop or master"
+	exit
+fi
+
+exe=$1
+branch=$2
+
+# Test if go is installed
+command -v go >/dev/null 2>&1 || { echo >&2 "Unable to find 'go'. This script requires go."; exit 1; }
+
+# Test if $GOPATH is set
+if [ "$GOPATH" == "" ]; then
+	echo "\$GOPATH not set"
+	exit
+fi
+
+echo "go get -u -d github.com/ethereum/go-ethereum/$exe"
+go get -v -u -d github.com/ethereum/go-ethereum/$exe
+if [ $? != 0 ]; then
+	echo "go get failed"
+	exit
+fi
+
+cd $GOPATH/src/github.com/obscuren/mutan
+git submodule init
+git submodule update
+
+echo "git checkout $branch"
+cd $GOPATH/src/github.com/ethereum/eth-go
+git checkout $branch
+
+cd $GOPATH/src/github.com/ethereum/go-ethereum/$exe
+git checkout $branch
+
+if [ "$exe" == "ethereal" ]; then
+	echo "Building ethereal GUI. Assuming Qt is installed. If this step"
+	echo "fails; please refer to: https://github.com/ethereum/go-ethereum/wiki/Building-Ethereum(Go)"
+else
+	echo "Building ethereum CLI."
+fi
+
+go install
+
+echo "done..."