Clarify deps installation instructions

Per discussion[^1], revert previous commit[^2] and clarify how to get
rakudobrew going The Right Way™ by updating the shim with `rehash` command.

[1] 1b3cf97#commitcomment-19334016
[2] 1b3cf97

Author: zoffixznet

README.md

@@ -21,13 +21,24 @@ to see the documentation for method `split` in class `Str`.
 
 ## Building the HTML documentation
 
-To build the documentation web pages, simply run
+Install dependencies by running the following in the checkout directory:
 
-    $ make html
+    panda installdeps .       # if you use panda
+    zef --depsonly install .  # if you use zef
+
+If you use [`rakudobrew`](https://github.com/tadzik/rakudobrew), also run the
+following, to update the shims for installed executables:
+
+    rakudobrew rehash
 
-In addition to the Perl 6 dependencies, you need to have `graphviz` installed.
+In addition to the Perl 6 dependencies, you need to have `graphviz` installed, which
+on Debian you can do by running
 
-Also install Pod::To::BigPage i.e. panda install Pod::To::BigPage then copy ~/.rakudobrew/moar-nom/install/share/perl6/site/bin/pod2onepage to ~/.rakudobrew/bin/
+    sudo apt-get install graphviz
+
+To build the documentation web pages, simply run
+
+    $ make html
 
 After the pages have been generated, you can view them on your local
 computer by starting the included `app.pl` program: