Make note pretty-formatted

Author: Morganov

book/01-introduction/sections/installing.asc

@@ -87,14 +87,19 @@ $ sudo apt-get install dh-autoreconf libcurl4-gnutls-dev libexpat1-dev \
   gettext libz-dev libssl-dev
 ----
 
-In order to be able to add the documentation in various formats (doc, html, info), these additional dependencies are required (Note: users of RHEL and RHEL-derivatives like CentOS and Scientific Linux will have to https://fedoraproject.org/wiki/EPEL#How_can_I_use_these_extra_packages.3F[enable the EPEL repository] to download the `docbook2X` package):
+In order to be able to add the documentation in various formats (doc, html, info), these additional dependencies are required:
 
 [source,console]
 ----
 $ sudo dnf install asciidoc xmlto docbook2X
 $ sudo apt-get install asciidoc xmlto docbook2x
 ----
 
+[NOTE]
+====
+Users of RHEL and RHEL-derivatives like CentOS and Scientific Linux will have to https://fedoraproject.org/wiki/EPEL#How_can_I_use_these_extra_packages.3F[enable the EPEL repository] to download the `docbook2X` package.
+====
+
 If you're using a Debian-based distribution (Debian/Ubuntu/Ubuntu-derivatives), you also need the `install-info` package:
 
 [source,console]