Added unit testing

[freave-public]

Changes proposed in this pull request:

• This merge request adds unit testing the CLI using the Mocha testing framework.
• Removed installers from the readme in favor of installing the CLI through NPM.
• Some minor refactoring of the services.
• Ignored .DS_STORE (MacOS)

[TLadd]

Ran into some errors when running the tests:

       should perform a http post call:

      AssertionError [ERR_ASSERTION]: Mocks not yet satisfied:
POST https://gateway.stackpath.com:443/cdn/v1/stacks/1/sites/2/scripts
      + expected - actual

      -false
      +true

      at Scope.done (node_modules/nock/lib/scope.js:155:10)
      at Object.finally (node_modules/fancy-test/lib/nock.js:30:29)
      at Context.run (node_modules/fancy-test/lib/base.js:59:36)

  2) service http
       should perform a http patch call:

      AssertionError [ERR_ASSERTION]: Mocks not yet satisfied:
PATCH https://gateway.stackpath.com:443/cdn/v1/stacks/1/sites/2/scripts/3
      + expected - actual

      -false
      +true

      at Scope.done (node_modules/nock/lib/scope.js:155:10)
      at Object.finally (node_modules/fancy-test/lib/nock.js:30:29)
      at Context.run (node_modules/fancy-test/lib/base.js:59:36)

  3) service http
       should throw a http error:

      AssertionError [ERR_ASSERTION]: Mocks not yet satisfied:
POST https://gateway.stackpath.com:443/error
      + expected - actual

      -false
      +true

      at Scope.done (node_modules/nock/lib/scope.js:155:10)
      at Object.finally (node_modules/fancy-test/lib/nock.js:30:29)
      at Context.run (node_modules/fancy-test/lib/base.js:59:36)

  4) service http
       should not throw a http error:
     AssertionError: expected [Error: An error occurred when connecting to StackPath host https://gateway.stackpath.com.] to not exist
      at Context.test_1.test.nock.it (test/services/http.test.ts:36:25)```