Add travis:encrypt command

[ryansch]

I took a pass at implementing the feature discussed in #8.

I exposed the --add and --override options to allow the end user to control edits to .travis.yml.

[laserlemon]

What does --split do? Should it be the default even though it isn't in the travis CLI?

[laserlemon]

I'd say let's pass our ENV variables as Travis accepts by default. I believe that's space separated. Unless there's an issue with that approach.

[ryansch]

That's the approach I started with and ran into issues with encrypt throwing exceptions because the data to be encrypted was too large. We have a lot of env vars.

[laserlemon]

This looks really good, thank you! 👏 I've been looking forward to this ability for a while now. I left some comments for us to discuss.

[ryansch]

I'll sync on this today.

[ryansch]

Instead of documenting all of the various travis encrypt options and being responsible for keeping them in sync with the parent project, I've instructed thor to pass any unknown options directly to the encrypt command.

[ryansch]

Apparently old versions of rails require thor 0.14.x. The feature I'm using to pass unknown options was only added in 0.17.0.

Do we really want to support any version of rails older than 3.2?

[ryansch]

The travis guys have taken things in a different direction with their new env var implementation. In lieu of this functionality, I've added a simple 'print' command to spit out a figaro environment's variables. I can then add them to .travis.yml, the website, or with travis env set.