handling errors properly

[AndyOGo]

fixes #61

[ahmadnassri]

only wrap the actual pug calls, not the whole logic block.

[AndyOGo]

Yeah that was my initial approach too.
Buuut, the nice thing about throw is that it "breaks" forEach like break does with a classic loop.
Hence I decided to wrap the whole block.
Otherwise we would need to accumulate errors in an array...

[AndyOGo]

Well, I prefer to bail-out on first error, but I can quickly change it to try all files.

[ahmadnassri]

can just call done() instead of using setImmediate given the new direction

[AndyOGo]

nope, setImmediate let's other i/o operations taking place before calling the next metalsmith plugin. see: https://nodejs.org/api/timers.html#timers_setimmediate_callback_args

[ahmadnassri]

need to add a test as well.

[AndyOGo]

here you go, a simple test to check if err is truthy

[AndyOGo]

@ahmadnassri
Are you happy with this PR?
If you insist on your suggestions, I really recommend not to do it for the above reasons.
Otherwise it's your baby, so I could still change it. For me it is very important to get this out asap.