Add quick install instructions and remove manual method.

Ahoy dear captain and distinguished members of the crew aboard. 

Now you can install Fisherman using, not one, but two methods!

The traditional, or "manual" method to install Fisherman. Still the one
favored by beefy old Fisherman with 💪 and heart.

    git clone https://github.com/fisherman/fisherman
    cd fisherman
    make

Or you can use the new hot, quick install method like a Fisherman
that communicates to sea creatures and can breathe under water.
He also carries a GE XM214 Machine Gun in one arm.

README.md

@@ -18,10 +18,8 @@ Other features include dependency management, great plugin search capabilities a
 
 ## Install
 
-```fish
-git clone https://github.com/fisherman/fisherman
-cd fisherman
-make
+```sh
+curl -L install.fisherman.sh | fish
 ```