doc: update reference section in userguide meta

Signed-off-by: jason taylor <jtfas90@gmail.com>

doc/userguide/rules/meta.rst

@@ -120,27 +120,28 @@ Our continuing example also has a classtype: bad-unknown:
 
 reference
 ---------
-The reference keywords direct to places where information about the
-signature and about the problem the signature tries to address, can be
+The reference keyword is used to document where information about the
+signature and about the problem the signature tries to address can be
 found. The reference keyword can appear multiple times in a signature.
 This keyword is meant for signature-writers and analysts who
 investigate why a signature has matched. It has the following format::
 
-  reference: type, reference
+  reference:type,reference
 
 A typical reference to www.info.com would be::
 
-  reference: url, www.info.com
+  reference:url,www.info.com
 
-However, there are also several systems that can be used as a reference. A
-commonly known example is the CVE-database, that assigns numbers to
-vulnerabilities. To prevent you from typing the same URL over and over
-again, you can use something like this::
+There are several systems that can be used as a reference. A
+commonly known example is the CVE-database, which assigns numbers to
+vulnerabilities, to prevent having to type the same URL over and over
+again. An example reference of a CVE::
 
-  reference: cve, CVE-2014-1234
+  reference:cve,CVE-2014-1234
 
 This would make a reference to http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-1234.
-All reference types are defined in the reference.config configuration file.
+
+All the reference types are defined in the reference.config configuration file.
 
 priority
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