Add new observables for displayed and dismissed states

[twittemb]

This commit add these new features:

• comment functions in UIViewController+Rx.swift file
• we can be triggered when a UIViewController:
  • is displayed for the first time
  • has a displayed state change (showed or hidden)
  • is dismissed
  • has its parents dismissed

[codecov-io]

Codecov Report

Merging #4 into swift-4.0 will decrease coverage by 0.44%. The diff coverage is 88.88%.

@@             Coverage Diff              @@
##           swift-4.0      #4      +/-   ##
============================================
- Coverage      92.75%   92.3%   -0.45%     
============================================
  Files              2       2              
  Lines             69      78       +9     
  Branches           6       7       +1     
============================================
+ Hits              64      72       +8     
  Misses             1       1              
- Partials           4       5       +1

Impacted Files	Coverage Δ
Sources/RxViewController/UIViewController+Rx.swift	88% <88.88%> (+0.19%)	:arrow_up:

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[devxoul]

Please don't change the indentation :(

[twittemb]

Hi,

I've just pushed a new version where code indentation has not changed.

[twittemb]

Hi. I changed my PR according to your remarks. It is pretty hard to test the difference between the dismissing/dismissed states in a XCTestCase. How would you do that ?

[devxoul]

Thanks! After some thoughts, isDismissed can be confused because it looks like that it is executed after the completion closure in dismissViewController(). I think we would better keep only isVisible and isDismissing.

[twittemb]

Hi, I've just pushed a new version. thx.

[devxoul]

Thanks for your contribution! :tada: