Add support for multiple match regexs

[Cadair]

Description

This PR adds the option to use regex.finditer to find all matches in the message string.

Status

UNDER DEVELOPMENT

Type of change

New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Unit tests

Checklist:

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (41246da) 99.16% compared to head (a0d21f5) 99.13%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2009      +/-   ##
==========================================
- Coverage   99.16%   99.13%   -0.04%     
==========================================
  Files          83       83              
  Lines        5395     5407      +12     
==========================================
+ Hits         5350     5360      +10     
- Misses         45       47       +2     

Files	Coverage Δ
opsdroid/parsers/regex.py	100.00% <100.00%> (ø)
opsdroid/events.py	96.46% <77.77%> (-0.92%)	⬇️

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.