Updated formatting on API.md

[elussich]

Note: the socket.io.js file is the generated output of make socket.io.js, and should not be manually modified.

The kind of change this PR does introduce

• a bug fix
• a new feature
• an update to the documentation
• a code change that improves performance
• other

Current behaviour

Formatting was broken on the Manager section, under "new Manager / options" object. It's not a big deal, but because of this, I was not being able to find the specific path property, which was critical for my own socket.io implementation.

New behaviour

path property will be displayed into a new line, as part of the properties list for the options object.

Other information (e.g. related issues)

The diff view may not show the actual results; you'd need to see the API.md as parsed html.

[darrachequesne]

Thanks!