Add support for S3 data sources

[andygrove]

Which issue does this PR close?

Closes #10

Builds on #289

Rationale for this change

For users on AWS, Ballista is not an option unless it supports S3.

$ ./target/release/ballista-cli --host localhost --port 50050
Ballista CLI v0.8.0
❯ CREATE EXTERNAL TABLE test (a int, b int) STORED AS CSV LOCATION 's3://andygrove-benchmark-data/test.csv';
0 rows in set. Query took 0.000 seconds.
❯ select * from test;
+---+---+
| a | b |
+---+---+
| 1 | 2 |
+---+---+
1 row in set. Query took 0.716 seconds.

What changes are included in this PR?

Are there any user-facing changes?

No

[yahoNanJing]

LGTM

[avantgardnerio]

Wow, thank you @andygrove , this makes my day considerably better!