Maintenance and Ruby 3.0
#178 Removes Jeweler
#213 Fix specs related to differences in Complex comparisons in Ruby 2.7
#211 Add support for Ruby 3.0 and general maintenance. Readme also updated.
Support for Ruby 2.3 and 2.4 has been dropped. This means that I will not be fixing bugs related to those ruby versions, and I will not be avoiding using language features added in 2.5+. At this point there are no known incompatibilities with older versions.