Update rc init scripts

- Move system specific setup to rc.$SYS scripts
- Write configure_ls function (based on previous anonymous function) that takes the full path to an ls binary
- Create system specific script for FreeBSD (nothing in it yet)

rc.darwin

@@ -0,0 +1,16 @@
+# .rc.darwin
+# vim: ft=zsh
+# Interactive shell setup for Darwin systems
+# Eryn Wells <eryn@erynwells.me>
+
+
+alias acls='command ls -le'
+
+# These things might have been installed by Homebrew, and I like the GNU versions better.
+binary_exists gdircolors    && alias dircolors='gdircolors'
+binary_exists gfind         && alias find='gfind'
+binary_exists gnuindent     && alias indent='gnuindent'
+
+if binary_exists gls; then
+    configure_ls `which gls`
+fi