documentation overhaul (#353)

* ident
* remove $Id$ tags from rcs software which has been retired
* make an effort to sync required mib docs with actual code
* sync even more docs with what code actually does
* some whitespace nits
* fixup example to use snmpv2 for all but the most ancient devices
* remove blurb to find more specific snmp::info classes for classes
  which alrdy are as specific as they can get (eg snmp::info::layer3::vmware
  doesn't need info on to find a specific module since there ain't none)
* rename all sub {vendor} strings to lowercase vendor, if cisco, juniper
  and arista can be lowercase, so can be all the rest.
* fix tests
* spread some use warnings around
* use $ instead of @
* remove defines that are included via parent classes
* use strict + warnings
* remove alrdy included modules
* add comma after last list item
* typos
* mibs are found in our mib repo, not on the cisco site
* documentation fixes

lib/SNMP/Info/Layer3/PaloAlto.pm

@@ -30,6 +30,7 @@
 package SNMP::Info::Layer3::PaloAlto;
 
 use strict;
+use warnings;
 use Exporter;
 use SNMP::Info::Layer3;
 
@@ -52,7 +53,7 @@ $VERSION = '3.68';
     # Oids from PAN-COMMON-MIB.
     'os_ver'     => 'panSysSwVersion',
     'serial1'    => 'panSysSerialNumber',
-    'pa_model'   => 'panChassisType'
+    'pa_model'   => 'panChassisType',
 );
 
 %FUNCS = (
@@ -64,7 +65,7 @@ $VERSION = '3.68';
 );
 
 sub vendor {
-    return 'Palo Alto Networks';
+    return 'palo alto networks';
 }
 
 sub model {
@@ -142,11 +143,11 @@ These are methods that return scalar value from SNMP
 
 =item $pa->vendor()
 
-Returns C<'Palo Alto Networks'>.
+Returns C<'palo alto networks'>.
 
 =item $pa->os()
 
-Returns C<'PANOS'>.
+Returns C<'PAN-OS'>.
 
 =item $pa->model()