Update Golang to 1.14, use Go Modules, drop support of Parallels Desktop 10 and OS X 10.10 Yosemite

[legal90]

Changes:

• Upgrade Golang to 1.14. That allows to use Go Modules - the latest approach for managing dependencies (see below)
• Migrate from godep to Go Modules for dependency management. That allows to get rid of keeping deps in vendor/*. More info: https://blog.golang.org/using-go-modules
• Update all dependencies
• Drop support of OS X 10.10 Yosemite and older. That's caused by the switching to go 1.14
• Drop support of Parallels Desktop 10. Since the beginning, there was an "unofficial" support of Parallels Desktop 10, but now we can cut it off because it reached the End-of-Life 3 years ago (since August 2017).

The changeset here is quite big, so I guess we will need to bump the major version of the provider after merging this PR