Raise a warning if a title row is found

Fixes #87

Needed for https://github.com/theodi/shared/issues/172

This raises a warning if the count of columns (discarding blanks) in the first row is less than the average count of columns in the rest of the CSV.

So, for example, this CSV:

![example](https://raw.github.com/theodi/R-projects/master/csv-stats/graphics/miss-header-example.png)

Will raise a warning of `title_row` (not sure if this should be an error actually).

We can then expand on this, and provide advice in the app