Add support for multipart form data via the request options

[FredKSchott]

(See original proposal here #924)

Summary

Instead of creating your own form for multipart uploads and having to append data separately, pass the data you'd like to attach via the request options argument. For more advanced cases where the third append argument is required, the current solution can still be used.

Before

// From README#Forms
var options = { /* ... */ };
var r = request.post(options, someOptionalCallback);
var form = r.form()
form.append('my_field', 'my_value')
form.append('my_buffer', new Buffer([1, 2, 3]))
// ...

After

var options = {
    url: 'http://service.com/upload',
    formMPU: {
        my_filed: 'my_value',
        my_buffer: new Buffer([1,2,3])
    }
};
request(options, someOptionalCallback);

[FredKSchott]

Forgot to mention in the PR, this includes tests for the new option.

[LoicMahieu]

+1 For this feature! It would be awesome!
Just... I am skeptical about the "formMPU" key ... Maybe "formdata" or something more representative. (Just a matter of vocabulary)

[crocket]

I also prefer "formdata" to "formMPU".
This makes multipart/form-data requests compatible with promisification.

[mikeal]

This try should be removed and form-data should be added to devDependencies.

[FredKSchott]

Re naming: In my original proposal I admitted I couldn't think of a good name :) I like formdata as well, I'll rename it.

[FredKSchott]

Hmm, Travis wasn't running test-form.js or test-form-data.js before because of that try-catch. Now that it's gone, it's having trouble finding the mime module, which is a normal dependency.

It looks like Travis isn't calling npm install before running your tests, which is preventing a lot of test suites from running.

[FredKSchott]

Also an open question: What should happen when form & formdata are present? Currently formdata takes precedence, but is this desired? (This should never really happen since both do conflicting things, but it is possible.)

[mikeal]

@FredKSchott there are lots of options that conflict when used together, i wouldn't worry about it too much :)

[mikeal]

you might wanna pull latest, the mime module was swapped for 'mime-types' and is updated in the test that is in HEAD.

[FredKSchott]

Ah, yea that was it. good catch.

Alright, comments addressed, tests passing, and README updated. Should be ready for final review / merge. Let me know if you need anything else, and feel free to edit the README if you'd rather explain the new option yourself.

[mikeal]

You know what, this should actually be a regular ol' dependency. I'm just not sold anymore on the optionalDependency thing, and making it a devDependency was not correct, that's my bad, I apologize :)

[FredKSchott]

No worries, I didn't even think about it either when I made the change

[mikeal]

one last comment/change cause I was wrong about the devDep :)

[nylen]

@mikeal would you be open to porting the test suite to mocha or similar?

[FredKSchott]

comment addressed

[mikeal]

This no longer merges cleanly and I think it refers to an old version of form data. Sorry this got lost in the pile would, love a clean PR though :)

[FredKSchott]

yea there's some wierdness going on here, I cleaned it up on my local repo but every pull request keeps including these other commits. I can't seem to fix it so I'll just keep it closed.

@crocket's PR looks fine, feel free to merge his instead.