Feat/improve perf

[loicmathieu]

This PR use the new methods on the FileSerde to improve the performance of the read/write of files.

Fixes #102

Here are some results running locally with the Google Cloud Storage internal storage implementation. The test read an ION file and wrote a file in the new format (scenario 'write'), then read the new format and write an ION fle (scenario read). Doing this for two kind of files:

• small: 1 million rows with 4 columns
• big: 100 thousand rows with approx. 150 columns

Excel and XMLS use fewer rows as they load the data in memory (small 100K and big 10K rows).

Format	Test	Before (s)	After (s)
Avro	write - small	11.7s	5.6s
Avro	read - small	6.6s	6.7s
CSV	write - small	12.5s	5.2s
CSV	read - small	6.8s	4.9s
CSV	write - big	14.8s	14.7s
CSV	read - bg	15.2s	14.9s
Excel	write - small	2.4s	1.9s
Excel	write - big	5s	5s
JSON	write - small	13.2s	16.6s
JSON	read - small	7.1s	6.1s
JSON	write - big	23.1s	21.7s
JSON	read - bg	20.5s	19.3s
Parquet	write - small	14.6s	7.3s
Parquet	read - small	8.4s	5.8s
XML	write - small	2.2s	2.3s
XML	read - small	1.6s	1.6s
XML	write - big	5s	4.9s
XML	read - bg	8.1s	8s