(py-goto-beginning-of-tqs): Finds the beginning of the triple quoted

(py-goto-beginning-of-tqs): Finds the beginning of the triple quoted
string we find ourselves in, based on the passed in delimiter.

(py-compute-indentation): Fixes for indentation errors when we land
inside a triple quoted string.  For example:

def foo():
   if os.path.isfile(o_pri_mbox_file) and os.path.isfile(o_pub_mbox_file):
       print """\
I found both a private and a public mbox archive file
    private: %s
    public : %s

I won't move either file, but you should choose one and move it to

    %s

You may want to merge them manually, but be careful about exposing private
correspondences to the public.""" % (
    o_pri_mbox_file, o_pub_mbox_file, mbox_file)
*----indentation would be wrong on this line.