Bug fixes on 0.2.2 + adding standard sql support + documentation

[lverzosa]

Hi everybody,

LMK if you need more info, but effectively I just made changes to 0.2.2. There were a lot of library conflicts with the latest versions of the libraries since then so I've reverted those changes back.

In this PR:

• Revert libraries to 0.2.2 version and scala back down to 2.11 (as 2.12 won't be supported until Spark 3.0)
• Fixed GoogleCredential for bigQuerySelect to use credentials file (in Json) provided by setGcpJsonKeyFile() instead of GoogleCredential.getApplicationDefault()
• Added flag for standard sql (while not breaking API for legacy SQL)
• Documentation changes (removed reference to Dataproc since I believe google provides an up to date connector that works on Dataproc)

Lorenz

[lverzosa]

Closed because I created a new PR that points to branch that isn't in active development