Update install instructions, closes #51

DESCRIPTION

@@ -12,7 +12,7 @@ URL: https://github.com/jeroen/v8 (devel)
   https://developers.google.com/v8/intro (upstream)
 BugReports: https://github.com/jeroen/v8/issues
 SystemRequirements: V8 version 6 or 7 is recommended, but 3.14 (legacy) is 
-    still supported as well. On Debian /Ubuntu you need either libv8-dev or 
+    still supported as well. On Debian / Ubuntu you need either libv8-dev or 
     libnode-dev, on Fedora use v8-devel.
 NeedsCompilation: yes
 VignetteBuilder: knitr

README.md

@@ -55,16 +55,20 @@ Binary packages for __OS-X__ or __Windows__ can be installed directly from CRAN:
 install.packages("V8")
 ```
 
-Installation from source on Linux requires [`libv8`](https://developers.google.com/v8/intro). On __Debian__ or __Ubuntu__ use either [libv8-dev](https://packages.ubuntu.com/bionic/libv8-dev) or for recent Debian you need [linode-dev](https://packages.debian.org/testing/libnode-dev):
+Installation from source on Linux requires [`libv8`](https://developers.google.com/v8/intro). On __Debian 10 (Buster)__ and up or __Ubuntu 19.04 (Disco)__ and up, use [linode-dev](https://packages.debian.org/testing/libnode-dev):
 
 ```sh
-# Most versions of Debian and Ubuntu
-sudo apt-get install -y libv8-dev
-
-# Alternatively for Debian Buster
+# Recent versions of Debian / Ubuntu
 sudo apt-get install libnode-dev
 ```
 
+On older versions of Debian/Ubuntu you need [libv8-dev](https://packages.ubuntu.com/bionic/libv8-dev):
+
+```sh
+# Older versions of Debian and Ubuntu
+sudo apt-get install -y libv8-dev
+```
+
 On __Fedora__ we need [v8-devel](https://apps.fedoraproject.org/packages/v8):
 
 ```sh