Nwparker/conv v2

[nwparker]

This PR introduces some major changes. It fixes many issues with the previous versions and changes some core functionality.

Changes in the PR:

• Re-written encoder (to deal with additional cases and data types)
• A decoder to convert from SparkSQL Rows back into the Java Thrift generated objects
• Supporting Additional Data Types
  • Map w/ complex (non-primitive) keys
  • Struct/Unions w/ self-recursive definitions (these will be converted to binary as there's no way to represent arbitrary recursive data types in SQL. A benefit of keeping in binary format is that the data can be decoded back into the original data structure with the decoder)
• A unit test to preserve the encode/decode invariant through (uses generated data via ScalaCheck)
• Thrift Java objects are no longer check into repo, but generated from Thrift sources
• Moves project from Maven to SBT (allows cross-building for multiple Scala versions)
• Updates Readme w/ some new info

Fixes #2

[liyintang]

@nwparker Thanks for making this change ! Let me take a look !

[nwparker]

Ah, I can remove this now that gen-java is written directly into /target

[nwparker]

@nwparker Thanks for making this change ! Let me take a look !

Hey @liyintang -- just wondering if you may have any update. Thanks!

[nwparker]

Another friendly bump ! 😄

[nwparker]

Bumping @liyintang -- & Happy Thanksgiving !

[nwparker]

bumping for the new year @liyintang

[nwparker]

Any update ?

[nwparker]

2020 bump