Insurance — General liability — Excess liability — Jurisdiction — Supplemental — Appellate court cannot exercise supplemental jurisdiction over appeal from district court’s grant of summary judgment to primary insurer on claim that primary insurer had unlawfully exposed insured to undue excess liability by prematurely exhausting its primary and umbrella general liability policy through its improper settlement allocations — Supplemental jurisdiction cannot provide the foundation for exercising jurisdiction over appeal, because district court lacked diversity jurisdiction over original complaint — There was an absence of complete diversity of citizenship, stripping district court of original jurisdiction, where excess insurer was named as party defendant in original complaint, district court was required to realign excess insurer as plaintiff since interests of original party plaintiff and excess insurer were coextensive at time of filing, and realignment of excess insurer as party plaintiff would have destroyed diversity since excess insurer and defendants were citizens of same state