pgloader - pgloader: Generalize unbuffered file reading to a file-like

Log Message:
-----------
Generalize unbuffered file reading to a file-like class and use it in csvreader and textreader. Almost ok now, or so it
seems

Modified Files:
--------------
    pgloader/examples:
        parallel.conf (r1.7 -> r1.8)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgloader/pgloader/examples/parallel.conf.diff?r1=1.7&r2=1.8)
    pgloader/pgloader:
        csvreader.py (r1.9 -> r1.10)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgloader/pgloader/pgloader/csvreader.py.diff?r1=1.9&r2=1.10)
        reader.py (r1.15 -> r1.16)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgloader/pgloader/pgloader/reader.py.diff?r1=1.15&r2=1.16)
        textreader.py (r1.16 -> r1.17)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgloader/pgloader/pgloader/textreader.py.diff?r1=1.16&r2=1.17)