add readme

Author: lonelyenvoy

README.md

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+# python-memoization
+A minimalist functional caching lib for Python
+
+## Usage in 2 lines
+
+```python
+def fun(arg):
+    return do_something_slow(arg)
+```
+
+Wanna caching this function? That's what you need:
+
+```python
+from memoization import cached
+
+@cached()
+def fun(arg):
+    return do_something_slow(arg)
+```
+
+Repetitive calls to ```fun()``` with the same arguments then run ```fun()``` only once.
+
+
+## Advanced topics
+
+### TTL (Time-To-Live)
+
+```python
+@cached(ttl=5)  # cache expires after 5 seconds
+def read_user_info(user):
+    return expensive_db_query(user)
+```
+
+For impure functions, TTL will be a solution.
+
+### Limited cache capacity
+ 
+```python
+@cached(max_items=1000)  # cache holds no more than 1000 items
+def get_compiled_binary(filename):
+    return a_very_large_object(filename)
+```
+
+When the cache is fully occupied, the data first came will be overwritten.
+
+
+## Contributing
+
+Any improvement or bug-fixing is welcome. Create a [pull request](https://github.com/lonelyenvoy/python-memoization/pulls) when you are done.
+
+## License
+
+[The MIT License](https://github.com/lonelyenvoy/python-memoization/blob/master/LICENSE)