Merge pull request #21 from TalLevAmi/master

Fix broken Cassandra::Future.all
[tests] check python and ccm presence when running tests
Merge pull request #22 from datastax/python-ccm-check

[tests] check python and ccm presence when running tests
[RUBY-34] return nil if a value is empty
[ci skip] update CHANGELOG
Merge pull request #23 from datastax/fix-timestamp-decoding

[RUBY-34] return nil if a value is empty
add a regression test for decoding empty buffer
[RUBY-36] default to token-aware dc-aware round robin
Merge pull request #24 from datastax/RUBY-36

Ruby 36
[ci skip] fix link description in the doc block
[RUBY-28] add heartbeating to detect broken connections
Merge pull request #25 from datastax/RUBY-28

Ruby 28
[RUBY-32] improve exception hierarchy and documentation
Merge pull request #26 from datastax/RUBY-32

RUBY-32
[RUBY-39] prevent usage of remote hosts by default
increase default heartbeat interval to 30 seconds
skip ignored hosts when waiting for schema agreement
[tests] demonstrate that remote hosts are not used
[ci skip] update CHANGELOG
Merge pull request #27 from datastax/RUBY-39

change defaults