Add sender level tags

[turtlespin]

Overview

This PR adds the concept of tags which can be set once against a RaygunSender instance and then applied to each exception which is raised through that sender. This avoids the requirement to specify tags with each invocation of send_exception.
A new method set_tags has been added to RaygunSender to allow these tags to be specified.

I have also updated the API endpoint to use api.raygun.com rather than api.raygun.io as part of this PR.

Examples

Setup

client = raygunprovider.RaygunSender('YOUR_API_KEY')

Initialize a client instance

client.set_tags(["process_tag1", "process_tag2"])

Use the new set_tags method to apply tags at a sender level

Example 1

client.send_exception(exc_info=(exc_type, exc_value, exc_traceback))

Raising an exception with no tags specified

The resulting error has the sender level tags applied

Example 2

client.send_exception(exc_info=(exc_type, exc_value, exc_traceback), tags={"tag1", "tag2"})

Raising an exception with tags specified

The resulting error has both the sender level tags and the instance level tags applied

Example 3

client.send_exception(exc_info=(exc_type, exc_value, exc_traceback), tags={"tag1", "tag1"})
client.send_exception(exc_info=(exc_type, exc_value, exc_traceback), tags={"tag3", "tag4"})

Raising 2 exceptions with different instance level tags specified

The 2 resulting errors both have the sender level tags applied but differ with the instance level tags that are applied

[darcythomas]

Side note: Do we have a matrix of features (like this) vs providers.

Something we could use to make small improvements to the providers, during our downtime etc.

[darcythomas]

I am not a fan of nulls (None) could this be an empty array (list?) instead.

[turtlespin]

Have updated to initialize as empty list