Format Darlingtonia log/stream output

[no-reply]

We want the log output to be formatted to include each message on a newline. To achieve this, we use a custom MessageStream to wrap STDOUT and format each message before appending it.

[coveralls]

Coverage increased (+0.02%) to 97.937% when pulling 492d8784ca5da75685c71c2d21af94c3a90b281d on format-messages into 5f5a4f7583d9e68a5960f6bc19ab70036945a1a9 on master.