Only use GREP_OPTIONS when it's not deprecated

Moddern versions of grep print:

> grep: warning: GREP_OPTIONS is deprecated; please use an alias or script

When GREP_OPTIONS is in use, so we'll only set it when it's allowed.

TODO: this might need some more testing

01_path

@@ -13,11 +13,11 @@ pathdirs=(
     /Applications/VMWare\ Fusion.app/Contents/Library
     $HOME/Applications/VMWare\ Fusion.app/Content/Library
     /Library/Frameworks/Python.framework/Versions/Current/bin
+    /usr/local/opt/coreutils/libexec/gnubin
     /usr/local/bin
     /usr/local/git/bin
     /usr/local/libexec/git-core
     /opt/local/bin
-    /usr/local/opt/coreutils/libexec/gnubin
     $HOME/bin
     $HOME/.rbenv/bin
 )

05_grep

@@ -3,6 +3,10 @@ if [[ -x `which ggrep` ]]; then
 	alias grep='ggrep --color'
 fi
 
+output=$(GREP_OPTIONS=test grep --version 2>&1)
+
+if [[ $output == ".*GREP_OPTIONS.*" ]]; then
 # From zsh-lovers: detect gnu grep:
-(grep --help 2>/dev/null |grep -- --color) >/dev/null && \
-export GREP_OPTIONS='--color=auto'
+        (grep --help 2>/dev/null |grep -- --color) >/dev/null && \
+        export GREP_OPTIONS='--color=auto'
+fi