Make vendor name configurable.

[greylabel]

No description provided.

[greylabel]

@grasmash -- can you kick Travis to test this again?

[grasmash]

I'm tempted to just replace the "acquia" in the template/composer.json with "your-organization". It's the only place that the variable would be used, so should we really make it a variable? Thoughts?

[grasmash]

Test has been kicked off again.

[greylabel]

@grasmash I agree this is a pretty trivial change, on the surface. I think the crux of the issue is whether we leverage a single file to hold project-specific config (project.yml), or if we are ok with config/variables/etc being spread throughout the BLT code and potentially undocumented. Personally, I would favor a more robust project.yml rather than need to make project-specific changes throughout the codebase.