Move PyHive requirement to extra

[jtcohen6]

resolves #109

Description

• sasl is an older package, not regularly maintained, and it's been bricking installs on a number of different systems
• It's a requirement of PyHive[hive], which is used for thrift and http connection methods.
• If a user wants to use the odbc connection method, that doesn't require PyHive at all. Today, inability to install sasl prevents them from being able to use the plugin.
• This PR moves PyHive to be an extra requirement, rather than primary one
  • Pro: easier for ODBC users
  • Con: breaking change for existing users, who will need to replace pip install dbt-spark with pip install dbt-spark[PyHive]
  • Neutral: moves thrift to be an extra as well, since it's only needed by the same connection types

Checklist

• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have updated the CHANGELOG.md and added information about my change to the "dbt next" section.

[kwigley]

looks good to me! pip install dbt-spark[PyHive] works for me! I tried to think of better keywords for these extras_require but nothing better came to mind.

[jtcohen6]

Thanks @kwigley! I can't think of a great name—thrift feels best, but then it's misleading that this is a requirement for the http method as well—so sticking with the underlying package name is at least precise.