Reads part of the README.rst for use as long_description in setup().

def read_readme():
    """
    Reads part of the README.rst for use as long_description in setup().
    """
    text = open("README.rst", "rt").read()
    text_lines = text.split("\n")
    ld_i_beg = 0
    while text_lines[ld_i_beg].find("start long description") < 0:
        ld_i_beg += 1
    ld_i_beg += 1
    ld_i_end = ld_i_beg
    while text_lines[ld_i_end].find("end long description") < 0:
        ld_i_end += 1

    ld_text = "\n".join(text_lines[ld_i_beg:ld_i_end])

    return ld_text