Made it possible for totalCount to be a promise

[rsolyanik]

An error occurs when trying to return a promise to totalCount

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Documented?	no
Fixed tickets	#286
License	MIT

[murtukov]

ping @mcg-web

Could you review this PR? I don't work with Relay, so I can't say if it's a good thing to allow to return a promise from the getter.

[murtukov]

@rsolyanik before pushing any changes you have to execute composer fix-cs to bring the code to predefined coding styles and composer static-analysis to check if there are any problems. If there are any problems, Travis-CI check won't pass. Also your branch is out-of-date with the current master, you either have to merge the master into your branch or rebase your branch onto current master and force-push it.

[rsolyanik]

ping @mcg-web

Could you review this PR? I don't work with Relay, so I can't say if it's a good thing to allow to return a promise from the getter.

This is necessary to load total counts via data loader in nested paged lists
Something like
{ customers(first: 1000) { edges { node { id, loyaltyAccounts { totalCount edges { node { .... } } } } } } }