Update symbolic links in pip-accel source index before every run
Pin pip-accel to pip < 1.5 (issues #22 and #23)

See issues #22 and #23 on GitHub:

 * --no-install option is deprecated for pip 1.5
   https://github.com/paylogic/pip-accel/issues/22

 * pip 1.5 error - need more than 2 values to unpack error
   https://github.com/paylogic/pip-accel/issues/23