Update fish configuration

- Add OS-specific config files
- Set JAVA_HOME automatically on OS X
- Disable fish greeting banner

fish/config.fish

@@ -13,6 +13,19 @@ if test -e ~/.config/fish/local.fish
   source ~/.config/fish/local.fish
 end
 
+# OS-specific configuration
+switch (uname)
+  case Linux
+    source ~/.config/fish/linux.fish
+  case Darwin
+    source ~/.config/fish/osx.fish
+  case '*'
+    echo 'Unknown OS. No specifc config'
+end
+
+# Disable Fish greeting banner
+set --universal fish_greeting
+
 # ========
 # Autojump
 # ========