triggering: correct length of index array

np.diff() ends up with shorter array by one item, numpy was always
silently expanding the index array so far but with 1.10 is showing a
deprecation warning and likely gonna raise in the future.

obspy/signal/trigger.py

@@ -346,7 +346,11 @@ def triggerOnset(charfct, thres1, thres2, max_len=9e99, max_len_delete=False):
     #
     on = deque([ind1[0]])
     of = deque([-1])
-    of.extend(ind2[np.diff(ind2) > 1].tolist())
+    # determine the indices where charfct falls below off-threshold
+    ind2_ = np.empty_like(ind2, dtype=bool)
+    ind2_[:-1] = np.diff(ind2) > 1
+    ind2_[-1] = False
+    of.extend(ind2[ind2_[:-1]].tolist())
     on.extend(ind1[np.where(np.diff(ind1) > 1)[0] + 1].tolist())
     # include last pick if trigger is on or drop it
     if max_len_delete: