Added the installer plugin

This plugin creates 2 aliases "in and up" that are system
and distro agnostic.   For example,
on Mac in = brew install
on SUSE in = sudo -E zypper install
on Debian in = sudo -E apt-get install
on RedHat in = sudo -E yum install

add the 'installer' to your plugin list in ~/.zshrc
source ~/.zshrc

now you can run
'in wget'
'up curl'

plugins/installer/README.md

@@ -9,7 +9,7 @@ On Debian/Ubuntu it's apt-get
 include the installer as a plugin in your ~/.zshrc
 
 to install a new app run
-install <app>
+in <app>
 
 you can upgrade an app with
-upgrade <app>
+up <app>

plugins/installer/installer.plugin.zsh

@@ -11,7 +11,7 @@
 source "${0:h}/core.sh"
 
 case $OS in
-    'mac') 
+    'mac')
         alias in='brew install'
         alias up='brew upgrade'
         ;;