Add more CSV format options

[shawnbot]

We're using fast-csv because it's the most featureful of the many CSV parsers out there. Here are some options we're not exposing yet:

• comment: Ignore rows prefixed with a certain character. I've seen CSVs that use #, but that's probably not a safe default.
• discardUnmappedColumns: "If you want to discard columns that do not map to a header."
• strictColumnHandling: "If you want to consider empty lines/lines with too few fields as errors"
• The parser also has trim, ltrim and rtrim options for removing whitespace around values.

[Downchuck]

I could also use an option to ignore malformed lines in csv data. One malformed line stopped up my parse, 'Error: Parse Error: expected: '"'"'