Feature/improve appsignal to support tagging

[Vuta]

background

We want to improve Appsignal logging by using tags for metric

design

• Check if the payload hash is in correct format (needs value and tags key), else returns failure result.
• Fallback to previous implementation if payload value is not a hash

test cases

• EventTracer.info action: 'Action', message: 'Message', appsignal: { increment_counter: { counter_1: 1, counter_2: 2 } } works as usual
• Tags can be added to metric with the format { name: { value: value, tags: hash } }
  Example:

    EventTracer.info(
      action: 'Action',
      message: 'Message',
      appsignal: {
        increment_counter: {
        counter_1: { value: 1, tags: { region: 'eu' } }
     }})

• Failure returns if tags are in invalid format (missing value and tags)

[hieuk09]

@Vuta could you bump the gem to 0.1.3. The changes look good to me.

[melvrickgoh]

@Vuta can u help to update this branch to incl. 0.2? I'll help to review the GH logs too

[hieuk09]

• tag is collected correctly

@Vuta could you bump this gem to 0.2.1?