In this commit file & daily-rotate-file add an 'error' event listener on
their stream so that we can emit those errors from the transport.

fixes winstonjs#511

This commit only deals with streams created by the transport.

Changes:
- Adds public property `maxRetries` -> defaults 2
- Adds internal property `failures` -> # of failed stream creation attempts
- Transport will attempt to re-create the stream on errors
- Will attempt to re-create while `failures < maxRetries`

This commit adds a conditional check to file / daily-rotate-file tranports
logging function. We check to make that the transport isn't currently in a
failed state (i.e failures >= maxRetries) if it is in a failed state then
we perform a NOOP and return an error to the logging callback.

changes:
- 2 tests added under file-test & daily-rotate-file-test
- 1 helper function added that is named `assertFailedTransport`