use */api.py for python module loading

for quick loading all regular used functions and classes of a module,
one can now use

    >>> from nextbiopy.io.api import *

It should be more structured now.
add read_fasta function

it has the same functionality sa nextbiopy.io.Fasta. Since some people
may use nb.io.read_fasta() instead of open()-like file reading.
add FASTQ parser, first try
add fastq related tests