Write readme Makefile target

`$ make readme` cleans up Redis, runs the doctests, then cleans up Redis
again.  This way, I don't have to pollute `README.md` with Redis cleanup
commands.

Makefile

@@ -76,6 +76,12 @@ else
 		python3 -m unittest --verbose $(tests)
 endif
 
+readme:
+	source $(venv)/bin/activate && \
+		python3 -c "from redis import Redis; redis = Redis(); print(redis.delete('dilberts', 'edible', 'expensive-function-cache', 'google-searches', 'lyrics', 'nextid:user-ids', 'printer', 'raj'))"; \
+		python3 -m doctest -v README.md; \
+		python3 -c "from redis import Redis; redis = Redis(); print(redis.delete('dilberts', 'edible', 'expensive-function-cache', 'google-searches', 'lyrics', 'nextid:user-ids', 'printer', 'raj'))"
+
 release:
 	rm -f dist/*
 	source $(venv)/bin/activate && \

README.md

@@ -36,14 +36,6 @@ That was the hardest part.
 
 ### Dicts
 
-Clean up for the doctest (ignore me):
-
-```python
->>> {redis.delete('raj'), 0, 1}
-{0, 1}
->>>
-```
-
 Create a `RedisDict`:
 
 ```python
@@ -72,14 +64,6 @@ True
 
 ### Sets
 
-Clean up for the doctest (ignore me):
-
-```python
->>> {redis.delete('edible'), 0, 1}
-{0, 1}
->>>
-```
-
 Create a `RedisSet`:
 
 ```python
@@ -112,14 +96,6 @@ False
 
 ### Lists
 
-Clean up for the doctest (ignore me):
-
-```python
->>> {redis.delete('lyrics'), 0, 1}
-{0, 1}
->>>
-```
-
 Create a `RedisList`:
 
 ```python
@@ -156,14 +132,6 @@ RedisList['everything', 'in', 'its', 'right', 'place']
 and even machines, without a single point of failure.  [Rationale and algorithm
 description.](http://antirez.com/news/102)
 
-Clean up for the doctest (ignore me):
-
-```python
->>> {redis.delete('nextid:user-ids'), 0, 1}
-{0, 1}
->>>
-```
-
 Instantiate an ID generator:
 
 ```python
@@ -207,14 +175,6 @@ description.](http://redis.io/topics/distlock)
 API as closely as is feasible.  In other words, you can use `Redlock` the same
 way that you use `threading.Lock`.
 
-Clean up for the doctest (ignore me):
-
-```python
->>> {redis.delete('printer'), 0, 1}
-{0, 1}
->>>
-```
-
 Instantiate a `Redlock`:
 
 ```python
@@ -304,14 +264,6 @@ In general, you should only use `redis_cache()` when you want to reuse
 previously computed values.  Accordingly, it doesn’t make sense to cache
 functions with side-effects or impure functions such as `time()` or `random()`.
 
-Clean up for the doctest (ignore me):
-
-```python
->>> {redis.delete('expensive-function-cache'), 0, 1}
-{0, 1}
->>>
-```
-
 Decorate a function:
 
 ```python
@@ -433,14 +385,6 @@ a margin of error up to 2%.  However, they can reasonably accurately estimate
 the cardinality (size) of vast datasets (like the number of unique Google
 searches issued in a day) with a tiny amount of storage (1.5 KB).
 
-Clean up for the doctest (ignore me):
-
-```python
->>> {redis.delete('google-searches'), 0, 1}
-{0, 1}
->>>
-```
-
 Create a `HyperLogLog`:
 
 ```python
@@ -512,14 +456,6 @@ particular element before, you really must never have seen it).  You can tune
 your acceptable false positive probability, though at the expense of the
 storage size and the element insertion/lookup time of your Bloom filter.
 
-Clean up for the doctest (ignore me):
-
-```python
->>> {redis.delete('dilberts'), 0, 1}
-{0, 1}
->>>
-```
-
 Create a `BloomFilter`:
 
 ```python