Return promise in initSessionService

[hitochan777]

Changes

• initSessionService now returns promise
• refreshFromLocalStorage also returns promise sessionService.loadUser().then(...) to guarantee that user is set to the redux state when the promise returned by initSessionService is resolved.
• beforeAll in index.spec.js calls done when the promise is resolved, instead of subscribing to redux store.

[hitochan777]

@bernabe9 I noticed that __setSession, __setUser and __setError modifies the global variables in localforage.js but you did not initialize them before each test. Maybe we should do so in order to make all the tests independent of the previous tests? Or did you do this intentionally for some reason? Thanks!

[coveralls]

Coverage remained the same at 97.842% when pulling dc36090 on hitochan777:return-promise into f3566dd on bernabe9:master.

[bernabe9]

Good work 💪

About the global variables in the tests you're right, we should initialize them before each test. So, maybe we could open a new PR later to improve those test.

[hitochan777]

@bernabe9 thanks for merging my PR! Yeah, definitely. we can work on it together.