Revert "Switch from list to deque for internal TM tape"

This reverts commit 3194bfc.
Deques indeed allow for efficient appendleft operations, however
item access performace is more important.

automata/tm/tape.py

@@ -1,8 +1,6 @@
 #!/usr/bin/env python3
 """Classes and methods for working with Turing machine tapes."""
 
-import collections
-
 
 class TMTape(object):
     """A Turing machine tape."""
@@ -17,7 +15,7 @@ def __init__(self, tape, **kwargs):
     def _init_from_tape_params(self, tape, *, blank_symbol, current_position=0,
                                position_offset=0):
         """Initialize a TM tape from the defined tape parameters."""
-        self.tape = collections.deque(tape)
+        self.tape = list(tape)
         self.blank_symbol = blank_symbol
         self.current_position = current_position
         self.position_offset = position_offset
@@ -41,7 +39,7 @@ def write_symbol(self, new_tape_symbol):
         """Write the given symbol at the current position in the tape."""
         actual_position = self.current_position + self.position_offset
         if actual_position == -1:
-            self.tape.appendleft(new_tape_symbol)
+            self.tape.insert(0, new_tape_symbol)
             self.position_offset += 1
         elif actual_position == len(self.tape):
             self.tape.append(new_tape_symbol)