Ar/support sorting by datetime

[amandawraymond]

Problem

Reported DateTime Issue

• failure to correctly paginate through records when sorting by a DateTime selector

Solution

ensure the serialization and deserialization via JSON of the Cursors handle the precision of DateTime data down to the nanosecond

Details

• bumped version to 0.3.1
• To be used via a forked version if not merged : Ar/support sorting by datetime callrail/rails_cursor_pagination#1
• removed failing workflow tests for ruby version 2.6

[aaronsama]

Hey @amandawraymond, thanks for your PR and sorry for the long delay in reacting to this. I opened #142 starting from this one and incorporating recent changes (Github wouldn't let me rebase properly). I made some changes but the overall logic remains the same.

I'll close this PR as a result.