Ch5: Fix python code in Priceline showdown example

[mbauman]

Name the "sp3" plot so it may be referenced in the label.
Fix indexing assignment error in showdown_loss() by creating a "close_mask"
intermediate boolean indexing variable.
Fix risk assignment -- values over by less than $250 were not being assigned the risk value. Ensure this happens by assigning loss[ix] = risk last.
Outputs and plots are not changed.

[CamDavidsonPilon]

Excellent changes. Thanks for spotting this bug; I'll pull and update the plots later today. One question, why include the sp3 variable, if it is never used later?

[mbauman]

Hm? sp3 is used in the current master. Lines 215 and 216:

  "sp3 = plt.fill_between(x , 0, norm_pdf( x, 12000, 3000), \n",
  "                color = \"#7A68A6\", lw = 3, alpha = 0.6,\n",
  "                 label = \"Trip price guess\")\n",
  "plt.autoscale( tight=True)\n",
  "p3 = Rectangle((0, 0), 1, 1, fc=sp3.get_facecolor()[0])\n",
  "legend([p3], [sp3.get_label()])"

[CamDavidsonPilon]

hmm yes haha. Thanks for pointing that out. Merging!