Fix plugins support

[RobLoach]

On line 12, plugins was a null variable, so no plugin was ever used:

var plugins = opts.plugins && Array.isArray(plugins) ? plugins : [plugins];

plugins undefined.

This will fix it, and no longer require the .filter call.

[tunnckoCore]

It won't allow to pass just single string as plugin, when only one plugin is needed. That's why didn't do it like that.

[RobLoach]

It's called plugins, which is plural. One would assume it would just take an array of plugins.

[tunnckoCore]

It's called plugins, which is plural.

Yes, right. But i think it also should accept string. We all can agree that we have tools that works in that way and it's normal to "just work" if someone pass just string - it's would be expected to work.

[ForbesLindesay]

The code before doesn't work at all in any case, so I'm merging this for now. Two things that can be discussed separately:

1. Should it accept a single item, rather than forcing you to create an array of one item? If not, it should probably error, rather than silently ignoring this case.
2. Should it accept strings, as an alternative to the actual plugin modules. I believe we do this with jstransformer-less.

[tunnckoCore]

The code before doesn't work at all in any case, so I'm merging this for now.

yea, noticed that before few weeks

Should it accept a single item, rather than forcing you to create an array of one item?

👍 yes, it should. And we should apply this strategy for all transformers that have "plugins" support.

[RobLoach]

#4
#2