Upgrade to Swift 5 (Krisiacik#224)

* Upgrade to Swift 5

- Fix test target
- Upgrade everything to Swift 5
- Fix compiler warnings
- Small refactor in VideoScrubber to DRY up code and fix warnings
- Update .travis.yml for Xcode 11
- Remove obsolete .swift-version file
- Bump version to 6.0.0

* Fix .travis.yml to use iPhone 11 simulator

Fixed typo on README. (Krisiacik#202)

* Fixed crash in iPad when we tap(Long press) on image viewer in full screen mode to share the image or video.

* Fixed typo on README.

* Removed unnecesary code.

Adding Podspec for Swift 4 support (Krisiacik#158)

* Bumping podspec

This is to incorporate the Swift 4 support that was merged into master.

* Updating podspec to 5.0.0

Since the Swift 4 upgrade was a breaking change, we're bumping this to 5.0.0 instead of 4.2.0.

* Updating README to reflect Swift 4/ImageViewer 5

Merge pull request Krisiacik#60 from JoeFerrucci/version-fix

Correct version

Added a nature based video.