improved error messages from walking someone through the steps

install.sh

 set -e
 
 if [ -z "$GOPATH" ]; then
-	echo \$GOPATH is unset: see https://golang.org/doc/code.html for details
+	echo Error: \$GOPATH is unset
+	echo See https://golang.org/doc/code.html for details, or try these steps:
+	echo -e "\tmkdir -p ~/go"
+	echo -e "\texport GOPATH=~/go"
 	exit 1
 fi
 
 EXPECTED_DIR=${GOPATH}/src/github.com/oragono/oragono
 
-if [ `pwd` != "$EXPECTED_DIR" ] ; then
-	echo working checkout is not where \$GOPATH expects it: should be $EXPECTED_DIR
+if [ "$PWD" != "$EXPECTED_DIR" ] ; then
+	echo Error: working directory is not where \$GOPATH expects it to be
+	echo "Expected: $EXPECTED_DIR"
+	echo "Actual:   $PWD"
+	echo See https://golang.org/doc/code.html for details, or try these steps:
+	echo -e "\tmkdir -p ${GOPATH}/src/github.com/oragono"
+	echo -e "\tcd ${GOPATH}/src/github.com/oragono"
+	echo -e "\tmv $PWD oragono"
+	echo -e "\tcd oragono"
 	exit 1
 fi