Bug fixes on OS X, add GNU readlink as deps #20

Makefile:
- short help was not properly created

love-release.sh:
- script aborts if GNU getopt is not found
- add GNU readlink as dependency, will check for greadlink too

README.md:
- add GNU readlink as dependency

love-release.sh

@@ -26,7 +26,7 @@ check_deps () {
     } && {
         unset GETOPT_COMPATIBLE
         local out=$(getopt -T)
-        if [[ $? -eq 4 && -z $out ]]; then
+        if (( $? != 4 )) && [[ -n $out ]]; then
             local opt=false
         fi
     }
@@ -34,6 +34,16 @@ check_deps () {
         >&2 echo "GNU getopt is not installed. Aborting."
         local EXIT=true
     fi
+    if ! command -v readlink > /dev/null 2>&1 || ! readlink -m / > /dev/null 2>&1; then
+        command -v greadlink > /dev/null 2>&1 || {
+            >&2 echo "GNU readlink is not installed. Aborting."
+            local EXIT=true
+        } && {
+            readlink () {
+                greadlink "$@"
+            }
+        }
+    fi
 
     command -v lua   > /dev/null 2>&1 || {
         echo "lua is not installed. Install it to ease your releases."