`io.open(...)` is preferred method over `codecs.open(...)`
removed unused or single use variables

This change includes minor fixes and code cleanup too.

This provides a fix to issue #131. The `split_unquoted_newlines()`
function added to the utils module handles the splitting of the string
by performing a simple iteration of the string passed in and splitting
on unquoted CR, LF, or CR+LFs as they are found.