Avoid multiple builds

[bguiz]

I have solved the problem that you describe here:

"One drawback of this is that if you have a build matrix that builds your project with multiple versions of your platform, you'll end up with the same number of pages builds. Which seems redundant."

Essentially, compare the build number to the job number, and allow only the first (or whichever index) to pass through. Example:

https://github.com/bguiz/plugin-registry/blob/59b0601d30ab8e75caaf9958aac4618277321cbd/.travis.yml#L17

Thanks for writing your blog post, BTW!

[jreyes33]

Another way to accomplish this is using deploy with an on conditional as described in the third example here: https://docs.travis-ci.com/user/deployment/#Examples-of-Conditional-Releases-using-on%3A