The current code base is not uniform. After some discussion,
we have chosen to go with double quotes by default.

`binds` is an array of a query attribute since Active Record 5.0.

Some tests does not work for unprepared statements.
Add `if ActiveRecord::Base.connection.prepared_statements` and fix a
regex for fix tests failure with `prepared_statements: false`.

This will allow eager type casting to take place as needed. There
doesn't seem to be any particular reason that the `in` statement was
forced for single values, and the commit message where it was introduced
gives no context.

See
https://github.com/rails/rails/commit/d90b4e2615e8048fdeffc6dffe3246704adee01f

`Computer` class needs to be require

See #17217 for more details

Rationale: this is more readable if serveral queries
are involved in one call. Also, it will be possible
to let AR log EXPLAINs automatically in production
mode, where queries are not even around.

The output in Travis is a bit different. The SQLite
documentation (http://www.sqlite.org/eqp.html) warns
output may change dramatically between releases. I
do not want to mock the result set because I want a
real EXPLAIN to happen. I prefer a test that may fail
in future releases than a test that may give false
positives in future releases.

This is a first implementation, EXPLAIN is highly
dependent on the database and I have made some
compromises.

On one hand, the method allows you to run the most
common EXPLAIN and that's it. If you want EXPLAIN
ANALYZE in PostgreSQL you need to do it by hand.

On the other hand, I've tried to construct a string
as close as possible to the ones built by the
respective shells. The rationale is that IMO the
user should feel at home with the output and
recognize it at first sight. Per database.

I don't know whether this implementation is going
to work well. Let's see whether people like it.