Designate header row when using from_xls or from_xlsx

[rdmurphy]

In our tx_salaries repo, we use csvkit (and by extension, now agate-excel!) to prep Excel files for processing. An extra option we also have — after the conversion has happened — is to peel off rows until we hit the header row. We always know where that header row is, so we can pass that index in and be good to go.

When I was doing some tests with agate-excel directly, I quickly hit that wall. It gets a little funky if an Excel spreadsheet has some useless extra rows before the data.

That sound like something that'd be worth having as part of the package? I imagine it could be another option to be passed into the from_ commands.

table = agate.Table.from_xlsx('i_dont_want_your_extra_rows.xlsx', header_row=4)

The biggest decision to make? Do you use zero-based indexing, or start at 1 like Excel? 😬 (We forget what we picked constantly.)

[jpmckinney]

Related wireservice/csvkit#669

[jpmckinney]

Also wireservice/csvkit#336