Merge pull request #440 from matthew-brett/fix-dft-old-pydicom

MRG: old Pydicom uses Decimal strings

Cast values to float before setting into nifti header.

Fixes error seen at
http://nipy.bic.berkeley.edu/builders/nibabel-py2.7-pyd0.9.7/builds/212

Author: matthew-brett

nibabel/dft.py

@@ -192,7 +192,8 @@ def as_nifti(self):
              (pdi * cosi[2], pdj * cosj[2], pdk * cosk[2], pos_1[2]),
              (0, 0, 0, 1))
 
-        m = numpy.array(m)
+        # Values are python Decimals in pydicom 0.9.7
+        m = numpy.array(m, dtype=float)
 
         hdr = Nifti1Header(endianness='<')
         hdr.set_intent(0)