[385] fix binary data encoding issue with tests

[cianmce]

Following on from issue: #385

Possibly also fixes #364

• Builds on PR: Enable adapter tests and disable broken Elasticsearch tests #386 where MySQL tests are enabled
• Force encoding of data to UTF-8
• Added tests for binary encoded data

Issue

We have been using Blazer with some tables that have binary UUID columns.
When returning data that has binary data and plain text data it raises an error.

e.g. running the following SQL with a MySQL data source

select unhex("F6"), 123

raises

Encoding::UndefinedConversionError - "\xF6" from ASCII-8BIT to UTF-8:

This only happens if

1. the binary column is the first column returned
2. there's no non-binary columns after the binary columns

e.g. these all work

select unhex("F6"); /* this works */
select unhex("F6"), unhex("F6"); /* this works */
select 123, unhex("F6"); /* this works */
select 123, unhex("F6"), 123; /* this works */

[ankane]

Hey @cianmce, thanks for reporting and the PR! It looks like it was due to the charting logic. Should be fixed in the commit above, but let me know if there are other queries that don't work.