add shebang to python scripts

for executing in the shell without call to python. Follows the example
of @kloudkl .

python/caffe/convert.py

@@ -1,3 +1,4 @@
+#!/usr/bin/env python
 """This script converts blobproto instances to numpy arrays.
 """
 

python/caffe/detection/detector.py

@@ -1,3 +1,4 @@
+#!/usr/bin/env python
 """
 Do windowed detection by classifying a number of images/crops at once,
 optionally using the selective search window proposal method.

python/caffe/drawnet.py

@@ -1,3 +1,4 @@
+#!/usr/bin/env python
 """Functions to draw a caffe NetParameter protobuffer.
 """
 

python/caffe/imagenet/wrapper.py

@@ -1,3 +1,4 @@
+#!/usr/bin/env python
 """wrapper.py implements an end-to-end wrapper that classifies an image read
 from disk, using the imagenet classifier.
 """