vision: support image URLs

[stephenplusplus]

Fixes #1239

Docs: http://stephenplusplus.github.io/gcloud-node/#/docs/master/vision?method=detect

To Dos

• Docs
• Tests
  • System
  • Unit

This change will allow our Vision API to accept image URLs.

vision.detectLogos('http://google.com/logo.png', function(err, logos) {
  logos = ['Google']
});

[coveralls]

Coverage decreased (-0.3%) to 99.716% when pulling c0f5573 on stephenplusplus:spp--1239 into 5199cad on GoogleCloudPlatform:master.

[jgeewax]

Is this supported? I thought it was just GCS URLs?

[stephenplusplus]

It's not supported by the Vision API. We just do a GET on the URL, get a base64 string of the contents, and pass that to Vision to be annotated.

[jgeewax]

Gotcha - can we make sure that's documented?

[stephenplusplus]

Definitely!

[coveralls]

Coverage remained the same at 100.0% when pulling 9eb59db on stephenplusplus:spp--1239 into 5771373 on GoogleCloudPlatform:master.

[stephenplusplus]

@callmehiphop ready for your review, sir.

[coveralls]

Coverage remained the same at 100.0% when pulling 25f56bf on stephenplusplus:spp--1239 into e9e4170 on GoogleCloudPlatform:master.