def from_plaintext path, fields
        Daru::IO.from_plaintext path, fields
      end
Read the database from a plaintext file. For this method to work,
the data should be present in a plain text file in columns. See
spec/fixtures/bank2.dat for an example.

== Arguments

* path - Path of the file to be read.
* fields - Vector names of the resulting database.

== Usage

df = Daru::DataFrame.from_plaintext 'spec/fixtures/bank2.dat', [:v1,:v2,:v3,:v4,:v5,:v6]