Bump version to 3.0.0

[OsamaSayegh]

Bumping the major version because 3e6f7e5 introduces a number of breaking changes to the abstract, memory and redis stores API, and also replaces the snapshot_limit config option with max_snapshot_groups and max_snapshots_per_group.

[codecov-commenter]

Codecov Report

Merging #526 (c639313) into master (3e6f7e5) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #526   +/-   ##
=======================================
  Coverage   87.48%   87.48%           
=======================================
  Files          18       18           
  Lines        1286     1286           
=======================================
  Hits         1125     1125           
  Misses        161      161           

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[nate-at-gusto]

@OsamaSayegh Push to rubygems.org coming soon?

[OsamaSayegh]

@nate-at-gusto yep, I think so! We need @SamSaffron to push it for us and I think he can do it tomorrow!

[SamSaffron]

sorry for the delay, pushed a new version of the gem just now!