add end to end tests for delimited text file reader/writer
enhanced file reader writer tests
Merge pull request #47 from lefthandmagic/delimitedtext_test

Add end to end tests for delimited text file reader/writer
Check upload policy every N messages / seconds

Reusing `secor.messages.per.second` which is used for rate limiting, but
we’re currently setting it to a very large number to avoid being rate
limited at all, so we might as well use it for this as well.