Update FailureDetector class of out_forward.rb

The method 'phi(now) of 'FailureDetector class calculates the variable 't wrong way.

When @heartbeat_interval is not the default value (1 sec), 't value contains @heartbeat_interval time. But 'mean doesn't. So @heartbeat_interval is set higher, 'phi(now) returns a higher value.
Add file permission parameter to each file creation. fixes #138

Non daemonized fluentd, create a file as 0644 permission.
But daemonized fluentd, create a file as 0666 or other permission.
It is caused by File.umask(0) at daemonize process,
so we should specify file permission for better permission management.
Merge pull request #143 from fluent/daemonize-permission

Add file permission parameter to each file creation. fixes #138
Merge pull request #140 from tsuda7/master

Calculation phi in out_forward.rb seems wrong.
fix to use fluent'd log event processing thread
to separate Engine.emit for $log from each plugin's main thread.

On current code, if Engine.emit on $log raises any exceptions, main thread of
each plugins (that calls logger) will fail and run into shutdown sequence.
This behavior is unexpected for many users.
Merge pull request #142 from tagomoris/log_event_thread

fix to use fluent'd log event processing thread
Add comments for e42ee4aa46564dbee3571ba134f9e5ddbfbda1ed commit
v0.10.35
fix to warn node detachment/recovering/standby-failover from info
Merge pull request #144 from tagomoris/warn_node_detection

fix to warn node detachment/recovering/standby-failover from info
Add .travis.yml
Add symlink_path option to point to latest written file. fixes #83
Goodbye incomprehensible code indent from plugins!
Add --dry-run option to check fluentd setup without actual run. fixes #145
Added encoding option
Revert "Added encoding option"

This reverts commit d2b118fb2611c0cad31d8c794aec09df8f755e98.
We regard the config file as written in UTF-8
add error class name on log
Merge pull request #147 from tagomoris/add_error_class

add error class name on log
Goodbye incomprehensible code indent from buffer.rb and output.rb