Edits for tutorial
Edits for tutorial

This patch is a follow-up to #101 and makes many minor edits in the tutorial text.

/cc sameeraxiomine

Author: Josh Rosen <joshrosen@databricks.com>

Closes #106 from JoshRosen/tutorial-edits.

snowflakedb/spark-snowflake,snowflakedb/spark-snowflake,snowflakedb/spark-snowflakedb,snowflakedb/spark-snowflakedb,snowflakedb/spark-snowflakedb