try to make echo usage as posix compliant as possible

setup.sh

@@ -1,5 +1,14 @@
 #!/bin/sh -e
 
+# Make sure that echo is posix compliant
+echo() {
+  if [ ! "$BASH_VERSION" = "" ]; then
+    /usr/bin/env echo -e "$@"
+  else
+    /usr/bin/env echo "$@"
+  fi
+}
+
 RC='\033[0m'
 RED='\033[31m'
 YELLOW='\033[33m'
@@ -14,11 +23,13 @@ if [ ! -d "$LINUXTOOLBOXDIR" ]; then
     echo "${GREEN}linuxtoolbox directory created: $LINUXTOOLBOXDIR${RC}"
 fi
 
-if [ -d "$LINUXTOOLBOXDIR/mybash" ]; then rm -rf "$LINUXTOOLBOXDIR/mybash"; fi
+if [ -d "$LINUXTOOLBOXDIR/mybash" ]; then
+  rm -rf "$LINUXTOOLBOXDIR/mybash"
+fi
 
 echo "${YELLOW}Cloning mybash repository into: $LINUXTOOLBOXDIR/mybash${RC}"
-git clone https://github.com/ChrisTitusTech/mybash "$LINUXTOOLBOXDIR/mybash"
-if [ $? -eq 0 ]; then
+
+if git clone https://github.com/ChrisTitusTech/mybash "$LINUXTOOLBOXDIR/mybash"; then
     echo "${GREEN}Successfully cloned mybash repository${RC}"
 else
     echo "${RED}Failed to clone mybash repository${RC}"
@@ -255,11 +266,11 @@ linkConfig() {
         touch "$CURRENT_BASHRC"
     fi
 
-    if cat "$CURRENT_BASHRC" | grep -q ". $GITPATH/.bashrc"; then
+    if grep -q ". $GITPATH/.bashrc" < "$CURRENT_BASHRC" ; then
         echo "Bash config is already being sourced${RC}"
     else
         echo "Appending to current bash config"
-        cat >> $CURRENT_BASHRC << EOF
+        cat >> "$CURRENT_BASHRC" << EOF
 
 ## ChrisTitusTech's bash config
 . $GITPATH/.bashrc