Support title-less CSVs

[waldoj]

Although CSV files are certainly supposed to have an initial row that consists of column names, that is not always so. Because CSV to API can be applied to remote datasets (and fairly encourages it, with its URL-based approach), it's reasonable to assume that people will be making APIs out of CSV files that they don't have the ability to modify. So it stands to reason that we should provide a mechanism to handle this. There's no method of doing this automatically, so we'll want to support a URL parameter that will cue CSV to API to generic automatic names for each column.

(Originally filed by @wdoerner as part of #17.)