* Adding replication lag metric

* Enable support for having the redis password in a file

* Update readme

* Add slave_port attribute to metric "redis_connected_slave_offset"

* run instructions

* add link to sample redis file

* fixed issue#221: apply correct key name while formatting debug log

Add Alpine Docker image

Shrink binary and image

treat string "err" as failure and return zero for gauge

bring back some accidentally dropped commits

fix query in dashboard

Cleanup some metrics

Remove `mem_fragmentation_ratio`:
* Comes from `redis_memory_used_rss_bytes / redis_memory_used_bytes`.
* Metric only provides 2 digits of accuracy compared to calculation.

Add allocator metrics.

Cleanup Prometheus naming of commands metrics names to avoid confusing
references to being a "Summary" metric, it's not.

Remove `total_system_memory`, this duplicates node_exporter metrics.

Signed-off-by: Ben Kochie <superq@gmail.com>

feat: add aof metrics

Update to tests to use Redis5, Golang 1.11 for tests and build

Add slowlog_last_id metric.

use codecov