Find a way to test with sqlite latest version in Travis

[tmylk]

Current sqlite version is 3.16

Some linux distributions have this version and we can't reproduce the issues reported in them because Travis is outdated.

We use Travis Ubuntu Trusty env with 3.8 version of sqlite. Travis Ubuntu Precise has 3.6. It also has an option to install sqlite 3.7.15 from a white-listed ppa which is not maintatined.

Suggested solution: create our own ppa with sqlite, white-list it in Travis, maintain it.

[piskvorky]

I thought the built-in sqlite module ships with Python (and its version is therefore a function of the Python version)?

[tmylk]

Sqlite does ship with Python but can also be updated at OS-level.