Update README.mkd

My rational for this is:
 1. Most linux desktop users are using some kind of debian/ubuntu/mint, so why not have them catered for primarily?
 2. the bash instructions work for everyone who has bash. Last time I checked, that was 99% of the linux community.

README.mkd

@@ -5,13 +5,13 @@
 ## Installation
 ```
     $ git clone git://github.com/tarruda/zsh-autosuggestions ~/.zsh-autosuggestions
-    $ sh ~/.zsh-autosuggestions/install
+    $ bash ~/.zsh-autosuggestions/install
 ```
 
-On some linux distributions like ubuntu and debian sh is symlinked to /bin/dash and causes an installation error since the installation script needs some bash features. If sh is symlinked to dash, please run it with the bash :
+If you do not have bash, please run it with sh :
 
 `
-bash ~/.zsh-autosuggestions/install
+sh ~/.zsh-autosuggestions/install
 `
 
 Any widget that moves the cursor to the right(forward-word, forward-char...)