Upgrade Swift 5 & fix warnings

[emrcftci]

Description

• Upgrade Swift version to 5

• Fix warnings related to Swift 5

Motivation and Context

• We will be compatible with the Swift 5,

• We will solve warnings

  after this pull-request merge.

What kind of change does this PR introduce?

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] File changes for improvement
• [x] This change requires a documentation update
• [x] I have run tests

[emrcftci]

Travis fails because of invalid options PTAL @tristanhimmelman 🚀 -> Travis CI invalid options issue

[emrcftci]

🚀 PTAL @gcharita

[ozgur]

any update on this?

[tristanhimmelman]

If you rebase this to get CI passing I will approve and merge