Allow configurable and dynamic s3 path

[arihantsurana]

Currently, the s3 loader writes files to a single s3 directory. This makes it somewhat hard to use with Athena or other hive query engines because we cannot set up time-based partitions by use of the directory structure. This also makes it harder to maintain and handle the data on s3.
Please allow optional configuration to load data onto s3 with a directory structure that can be filled with values from s3 loader's server timestamp.
eg. -

configure to store in monthly chunks:
s3_path = "base_dir/enriched/good/yr={YYYY}/mo={MM}"

store in base directory:
s3_path = "some_dir/raw"

store in hourly chunks:
s3_path = "base_dir/enriched/good/date={YYYY-MM-dd}/hour={HH}"

[arihantsurana]

Added PR to solve for this - #135