Merge pull request #1 from gregmalcolm/master

sync
about_lists: pop(0) vs popleft() in 2vs3

I've looked for information on this note and haven't been able to find
anything of the sort.

A brief test in Py3.4.1 also indicates that list.pop(0) vs
deque.popleft() performance in Py3 is consistent with Py2.

>>> import timeit
>>> timeit.timeit('''x = list(range(100000))
while x:
x.pop(0)
''', number = 100)
385.9676046228002
>>> timeit.timeit('''x = deque(range(1000000))
while x:
x.popleft()
''', setup = 'from collections import deque', number = 100)
17.6067819813139
Merge pull request #102 from irheart/master

Note on list.pop(0) in Python 2 vs Python 3 in about_lists