Feature/addhost ip validation

[hishamanver]

Changed:

• fix install requires - should be a list object
• support multihoming ip avp validation
• Cleanup whitespaces (apologies for this, my editor does this automatically, happy to revert if required)

Why:

• install dependencies is broken as there is a missing comma between pyyaml and pysctp
• I am using bromelia as a client to test against a real HSS, the HSS returns 3 host addresses in the CEA, with the current code, the CEA verification fails as IP host validation accepts all three IP addresses thus making the checklist_mandatory_avps variable (https://github.com/heimiricmr/bromelia/blob/master/bromelia/process.py#L361) get a value of +2, these changes will set the ip valid counter only once and then finally tally up the mandatory avps

includes changes from #18