feat: update client to 1.8.0 (#17)

Author: bednar

CHANGELOG.md

@@ -3,6 +3,9 @@
 ### API
  1. [#15](https://github.com/influxdata/influxdb-plugin-fluent/pull/15): Default port changed from 9999 -> 8086
 
+### Dependencies
+1. [#16](https://github.com/influxdata/influxdb-plugin-fluent/pull/16): Upgrade InfluxDB client to 1.8.0
+
 ## 1.5.0 [2020-07-17]
 
 1. [#12](https://github.com/influxdata/influxdb-plugin-fluent/pull/12): Renamed gem to `fluent-plugin-influxdb-v2`

fluent-plugin-influxdb-v2.gemspec

@@ -47,7 +47,7 @@ Gem::Specification.new do |spec|
   spec.required_ruby_version = '>= 2.2.0'
 
   spec.add_runtime_dependency 'fluentd', '~> 1.8'
-  spec.add_runtime_dependency 'influxdb-client', '1.6.0'
+  spec.add_runtime_dependency 'influxdb-client', '1.8.0'
 
   spec.add_development_dependency 'bundler', '~> 2.0'
   spec.add_development_dependency 'codecov', '~> 0.2.8'