Small errors corrected in our LP/IP examples

Two small errors in our LP and IP examples have been corrected thanks to remarks of two students:

Errors corrected:

• Small error in one constraint of the "product line investment" removed, thanks to the remark of Pu Linyan (Peking University, International MBA (China)).
• Small error in the solver of the "floataway tours problem" solved, thanks to the remark of Thomas Lettens (Vlerick Business School (Belgium)).