feat(GraphQLTemplate) option to externalize fetching, Relates #70

[jleibund]

Allow fetching to be externalized when necessary.

[coveralls]

Pull Request Test Coverage Report for Build 93

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.004%) to 99.057%

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Totals
Change from base Build 91:	0.004%
Covered Lines:	525
Relevant Lines:	530

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💛 - Coveralls

[chemdrew]

looks great, thanks for the contribution! Could you please resolve the conflicts, @jleibund?