Expiringsqlitedict

* Remove the serializer ABC.
* Use WAL, serialized=NORMAL, and optimize the database on close.
* Allow serializers to use many types, instead of just bytes.
* Allow non-class serializers, like the json module (and other similar modules).
* Change default serializer to json.
* Use cursors for all operation, instead of the implicit db.execute.
* Allow customizing transaction type, defaulting to IMMEDIATE.
* Make a SqliteDict.close method, so the user doesn't have to wait until program
exit.
* Add a OnDemand, allowing opening a SqliteDict, entering it, and closing
it in one context manager that is reentrant. The use of it is the same, but
it won't open until needed and will immediately close when done with.

* Fill type hints through all parts of module

* Completely rewrite module to rely on sqlite3 internals as much as possible.

* Add encode and decode parameters to store json, compressed or pickled objects (erosennin, 65)
* Python 3.6 fix: commit before turning off synchronous (bit, 59)
* Update sqlite version to 3.8.2 (tmylk, 63)

* Fix some hangs on closing. Let __enter__ re-open a closed connection. (ecederstrand, 55)
* Surround table names with quotes. (Digenis, 50)

* Read-only mode (nrhine1, 37)
* Check file exists before deleting (adibo, 39)
* AttributeError after SqliteDict is closed (guyskk, 40)
* Python 3.5 support (jtatum, 47)
* Pickle when updating with 2-tuples seq (Digenis, 49)
* Fix exit errors: TypeError("'NoneType' object is not callable",) (janrygl, 45)