Revert some changes causing performance regression

fretbursts/burstsearch/burstsearchlib_c.pyx

@@ -10,12 +10,12 @@ To compile run::
     python setup.py build_ext --inplace
 
 """
-from builtins import range, zip
 
 import sys
 import numpy as np
 cimport numpy as np
 
+
 cdef pprint(s):
     """Print immediately, even if inside a busy loop."""
     sys.stdout.write(s)
@@ -49,13 +49,14 @@ def bsearch_c(np.int64_t[:] t, np.int16_t L, np.int16_t m, np.float64_t T,
     """
     cdef int i, i_start, i_end
     cdef np.int64_t burst_start, burst_end, t1, t2
-    cdef np.int8_t[:] above_min_rate = np.empty(t.size - m + 1, dtype='int8')
+    cdef np.int8_t[:] above_min_rate = np.empty(t.size - m + 1,
+                                                dtype=np.int8)
     cdef np.int8_t in_burst = False
 
     if verbose: pprint('C Burst search: %s\n' % label)
     bursts = []
 
-    for i in range(t.size-m+1):
+    for i in xrange(t.size-m+1):
         if (t[i+m-1] - t[i]) <= T:
             if not in_burst:
                 i_start = i
@@ -105,7 +106,7 @@ def mch_count_ph_in_bursts_c(mburst, Mask):
         for i,b in enumerate(bursts):
             # Counts donors between start and end of current burst b
             #num_ph[i] = mask[b[iistart]:b[iiend]+1].sum()
-            for ii in range(b[iistart],b[iiend]+1):
+            for ii in xrange(b[iistart], b[iiend]+1):
                 num_ph[i] += mask[ii]
             #count_ph_in_bursts(bursts, mask).astype(float)
         Num_ph.append(num_ph.astype(np.float))