fix #66 (proper executing state handling)

[stefanomondino]

This also updates dependencies to latest versions.

[ashfurrow]

This is great! Thanks for the PR and detailed issue. @ishkawa when you have a chance, could you look this over? You're most familiar with that part of the code.

[ishkawa]

Thank you for the PR.
I'll review this today.

[ishkawa]

I think shareReplay(1) should be placed after startWith(false) so that late subscribers can received the latest value as an initial value, not fixed false.

executing = Observable
    .of(executionStart.map { _ in true }, executionEnd.map { _ in false })
    .merge()
    .startWith(false)
    .shareReplay(1)

[ishkawa]

Could you run carthage bootstrap --use-submodules --no-build and commit submodule updates? CI job gets dependencies via git submodule update --init, not via carthage bootstrap, so we have to synchronize Carthage.resolved and .gitmodules.

Expected git status output look like below:

modified:   Carthage/Checkouts/Nimble
modified:   Carthage/Checkouts/Quick
modified:   Carthage/Checkouts/RxSwift

[fpillet]

This PR really should be split in two. One part touches test frameworks, the other is unrelated and touches code

[fpillet]

@stefanomondino would you mind closing this PR and opening another one with just the test frameworks / carthage module updates ? Thanks!