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

xt/lib/My/Test/Class.pm

@@ -29,6 +29,8 @@
 
 package My::Test::Class;
 
+use strict;
+use warnings;
 use Test::Class::Most attributes => [qw/class mock_session todo_methods/];
 use Test::MockObject::Extends;
 use File::Find 'find';
@@ -36,7 +38,7 @@ use Path::Class 'dir';
 use File::Slurper 'read_lines';
 use Class::Inspector;
 
-use base qw<Test::Class Class::Data::Inheritable>;
+use base qw/Test::Class Class::Data::Inheritable/;
 
 # Don't run the base tests defined in this class, run them in subclasses only
 My::Test::Class->SKIP_CLASS(1);