Determine how Babili should be versioned

[Daniel15]

See https://github.com/babel/babili/issues/139

Currently each plugin has its own version number, which makes it difficult to version babili-standalone as a whole.

cc @hzoo

[hzoo]

Right now the preset/cli will update with every update in lock-step so it should be ok to version based on the preset only?

[Daniel15]

@hzoo Ahh I see, so I should be fine just using the version number of the preset? Is there any case where a plugin would have its version number updated but the preset wouldn't be updated?

[Daniel15]

@hzoo - Currently babel-preset-babili is at 0.0.8 but babel-plugin-minify-dead-code-elimination is at 0.1.0, so I don't think I can just rely on the version number of the preset.