Make sure S3 directory paths are suffixed with '/' on creation
[FLINK-1186] Fix wrong flat key position when using expression key for nested tuples

This closes #169
[FLINK-1323] Refactor I/O Manager Readers and Writers to interfaces, add implementation that uses callbacks on completed write requests.

 - This change also allows for a very simple way of plugging in a synchronous version of the I/O manager.

This closes #193.
[FLINK-983] Fix WebClient truncated function names

This closes #190.
[FLINK-1223] Allow value escaping in CSV files

- Strings can now contain " quoted characters
- Skip trailing whitespace after quote

This closes #187.