Fixed issue 63.

Fixed the line
       
 self.Q_fe = self.Q_fe = float(sqrt(Integer(self.conductor))/2.**len(self.nu_fe)/pi**(len(self.mu_fe)/2.+len(self.nu_fe)))

by changing the divisions by 2 to division by 2. (i.e. floating point).
Integer division returns an int and so, for odd len(self.mu_fe), the
above was producing wrong powers of pi.