Writes data to a csv file.
If target-dir does not exists, it is created before saving. File content
in data should be represented as a sequence of sequences of strings. The
data is stored by rows. File is saved to [target-dir]-[file-name].
Returns an absolute path to the target-dir.

## Usage

   (require '[utilities.writer :refer :all])

   (csv-file "folder"
             "file.csv"
             [["header 1" "header 2"]
              ["row_1_col_1" "row_1_col_2"]
              ["row_2_col_1" "row_2_col_2"]])

Writes data to a text file.
If target-dir does not exists, it is created before saving. File content
in lines should be represented as a sequence of strings. File is saved
to [target-dir]-[file-name].
Returns an absolute path to the target-dir.

## Usage

   (require '[utilities.writer :refer :all])

   (txt-file "folder"
             "file.asc"
             ["line 1"
              "line 2"
              "line 3"])