Don't append to a truncated line in the journal.

Fixes https://github.com/square/okhttp/issues/1099
Merge pull request #1100 from square/jwilson_1023_rebuild

Don't append to a truncated line in the journal.
Log uncaught IOExceptions instead of rethrowing them.

The application layer can handle these with a try/catch block in their
onResponse method if desired.

This prevents a crash for applications that haven't deliberately configured
their uncaught exception handlers.

Closes https://github.com/square/okhttp/issues/1049
Merge pull request #1103 from square/jwilson_1025_log_failures

Log uncaught IOExceptions instead of rethrowing them.
Add an accessor, Call.isCanceled().

Closes https://github.com/square/okhttp/issues/912
Merge pull request #1104 from square/jwilson_1025_isCanceled

Add an accessor, Call.isCanceled().