Issue #50: reimplement logging.

• Initialize it by setting the logging level you want displayed.
• Create Log outputs with a level for when it should be displayed.
• Set file output.

I didn't write any logging in the copying part since that will be affected by the Redis Pipeline change.

I set it to 3 output levels because I thought that seemed reasonable. Another option could be to have different categories, like Reads, Writes, Actions, etc.

Describe the solution you'd like

Provide a docker compose solution so a maintainer or user can run this box in isolation of needing PostgreSQL/MySQL and Redis to test this.

Describe alternatives you've considered

A docker image could be appropriate for testing which combines Go, MySQL, PostgreSQL and/or Redis in one box, however it would require maintenance of upstream Docker images and there's no performance penalty using docker compose, a docker-compose template allows maintainers to just completely retrash/rebuild their development environment by services.

Expected Behavior

• The highlighted list item should be removed as I've since removed logging entirely from the library.

Current Behavior

• The highlighted list item is not removed

To solve issue #45

before data pipelining

> go test -v -db mysql -rows 10000
Preparing Test...
=== RUN   TestCopyToString
--- PASS: TestCopyToString (11.00s)
=== RUN   TestCopyToList
--- PASS: TestCopyToList (1.25s)
=== RUN   TestCopyToHash
--- PASS: TestCopyToHash (1.25s)
PASS
ok      github.com/DGKSK8LIFE/redisql   18.056s

after data pipelining

> go test -v -db mysql -rows 10000
Preparing Test...
=== RUN   TestCopyToString
--- PASS: TestCopyToString (1.31s)
=== RUN   TestCopyToList
--- PASS: TestCopyToList (1.05s)
=== RUN   TestCopyToHash
--- PASS: TestCopyToHash (1.15s)
PASS
ok      github.com/DGKSK8LIFE/redisql   7.865s

Expected Behavior

Performance in CopyToString should be comparable to that of CopyToList and CopyToHash.

Current Behavior

CopyToString is over 100% slower than the aforementioned two.

Possible Solution

Because of Redis' data structures, CopyToString (strings) has to write one key per field, compared to CopyToList and CopyToHash that both write one key per row. This is not necessarily something that can be "quick fixed", but with other performance optimizations, especially transactions and pipelining, performance should improve drastically.

Steps to Reproduce

1. Run test cases with ~10k rows or so and your preferred DB.
2. View output:

➜  redisql git:(master) go test -v -db mysql -rows 10000 
Preparing Test...
=== RUN   TestCopyToString
--- PASS: TestCopyToString (8.43s)
=== RUN   TestCopyToList
--- PASS: TestCopyToList (0.75s)
=== RUN   TestCopyToHash
--- PASS: TestCopyToHash (0.92s)
PASS
ok      github.com/DGKSK8LIFE/redisql   17.995s