Fix test failure at in_object_space.

Depending on GC timing, mock object at test/mixin.rb are remains while
test/in_object_space.rb. But lib/fluentd/in_object_space.rb call Object#class
on all un-GCed object, including mock object.

Because unexpected method expectations are happen, in_object_space reports failure.
Fix failure when calling Object#class.

Object#class is not always success.
E.g. a dead actor of Celluloid are failed with any method call.
Merge pull request #58 from mzp/fix_in_object_space

Fix in_object_space
in_tail: update inode in a PositionEntry when a log file rotated
added in_debug_agent and fluent-debug command
fluent-debug: fix to recognize command-line options and show connected uri
fix listen address for configuration not to bind "localhost"
add secondary groups to the process when changing process user
Ruby prefers ? rather than if-then
out_forward: assumes getting a heartbeat after send_data
out_forward: lazier failure detection: default phi_threshold 8 -> 10
in/out_forward: include \0 in heartbeat packets
there might be one or two spaces between month and day for syslog date format
in_syslog: allocates 2048 bytes for a read buffer
Merge pull request #67 from thbishop/inherit_secondary_groups_when_changing_process_user

Add secondary groups to the process when changing process uid
in_tail: seek to saved position if rotated file has the same inode number with the last file
Merge branch 'master' of github.com:fluent/fluentd
in_tail: added MemoryPositionEntry which replaces NullPositionEntry to detect 'rotated file has the same inode number with the last file' situation
Merge pull request #65 from mzp/fix_fluent_debug

fix fluent-debug to recognize command-line options
in_tail: error during Engine#emit should not close input file