BF: include forgotten dipy.utils (used by other modules)
BF: include forgotten dipy.utils (used by other modules)

$> make testinstall-dipy
 I: install nibabel done
 I: install nipy    done
 I: install dipy    done
 I: testinstall dipy
< ./utils/__init__.py
< ./utils/tripwire.py

that leads to failure of building examples against 'installed' dipy (i.e. not
within the source tree):

/home/yoh/proj/nipy/nipy-suite/install/lib/python2.6/site-packages/dipy/data/tracks300.trk
Traceback (most recent call last):
  File "../tools/make_examples.py", line 82, in <module>
    execfile(script)
  File "file_formats.py", line 52, in <module>
    from dipy.io.dpy import Dpy
  File "/home/yoh/proj/nipy/nipy-suite/install/lib/python2.6/site-packages/dipy/io/dpy.py", line 14, in <module>
    from ..utils.tripwire import TripWire, is_tripwire
ImportError: No module named utils.tripwire
make[1]: *** [rstexamples-stamp] Error 1
make[1]: Leaving directory `/home/yoh/proj/nipy/nipy-suite/dipy/doc'

sinkpoint/dipy,nilgoyyou/dipy,maurozucchelli/dipy,FrancoisRheaultUS/dipy,beni55/dipy,Messaoud-Boudjada/dipy,mdesco/dipy,villalonreina/dipy,JohnGriffiths/dipy,StongeEtienne/dipy,rfdougherty/dipy,samuelstjean/dipy,FrancoisRheaultUS/dipy,maurozucchelli/dipy,samuelstjean/dipy,demianw/dipy,mdesco/dipy,maurozucchelli/dipy,oesteban/dipy,Messaoud-Boudjada/dipy,StongeEtienne/dipy,sinkpoint/dipy,villalonreina/dipy,matthieudumont/dipy,jyeatman/dipy,nilgoyyou/dipy,beni55/dipy,demianw/dipy,matthieudumont/dipy,jyeatman/dipy,oesteban/dipy,rfdougherty/dipy,JohnGriffiths/dipy,samuelstjean/dipy