detect tab delim files with .csv extensions

[raprasad]

• detection is "dumb", assumes files ending in ".csv" are comma delimited
• many ".csv" files sent during testing by other groups were actually tab delimited
• check header row when ".csv" is detected.

[raprasad]

example file that's tab-delim csv: http://metadata.2ravens.org/preprocess/api/metadata/102/version/1.0?pretty