Support for Swift Package Manager

[tycobbb]

Adds support for Swift Package Manager. Picking up where #73 left off. Closes #67.

[loudmouth]

hey @wzrad

I fixed my PR #73
Apologies for the delay. As noted in my last comment, DVR still won't work in running tests from the command line with the swift cli until SPM supports bundling non Swift resource files (i.e. the JSON that DVR uses for fixtures).

Wanna upvote these two (duplicate) tickets on SPM?
SR-2866
SR-4725

[tycobbb]

@loudmouth

awesome, i will close this then :)