add preliminary support for exinda / gfi traffic shapers (#283)

* exinda support

* exinda support

* add exinda hint

needed to identify exinda devices.

* mentin exinda in overview and link docs

* overwrite layers to l2/3/4/7

* get uptime from exinda mib

now matches uptime reported by cli & web interface.

* single quotes preferred

* to much copy/paste

* merge 3.63

* some more functions added. also general cleanup

* Update .travis.yml

* a few fixes

* Update .travis.yml

* Update .travis.yml

* revert

* revert

MANIFEST

@@ -54,6 +54,7 @@ lib/SNMP/Info/Layer2/Catalyst.pm
 lib/SNMP/Info/Layer2/Centillion.pm
 lib/SNMP/Info/Layer2/Cisco.pm
 lib/SNMP/Info/Layer2/CiscoSB.pm
+lib/SNMP/Info/Layer2/Exinda.pm
 lib/SNMP/Info/Layer2/HP.pm
 lib/SNMP/Info/Layer2/HP4000.pm
 lib/SNMP/Info/Layer2/HPVC.pm