Can register conditions in which the running loop continues/stops

Test cases can register post conditions that will have to be all
satisfied at the end of the loop, and breaking conditions that are to
exit the running loop. If all of the post conditions are true or any of
the breaking conditions is true, the running loop stops.
To avoid infinite loop, timeout are registered as a breaking condition
before the loop starts running.
Merge pull request #415 from salty-g/master

Implement 'disable_retry_limit' output option.
Refactoring of SetTagKeyMixin and SetTimeKeyMixin.
Merge pull request #411 from baschtl/better-configurable-time-key-and-tag-key-mixins

Refactor time key and tag key mixins
v0.10.53
Update Cool.io dependency to 1.2. fixes #419
Merge pull request #420 from fluent/update-cool.io-to-1.2

Update Cool.io dependency to 1.2. fixes #419
Update msgpack dependency to 0.5
Merge pull request #421 from fluent/update-msgpack-to-0.5

Update msgpack dependency to 0.5
Forget to add blocking_timeout to in_stream. refs #419
Remove older rubygems support
Use v1 configuration by default
Unify License term
example configs for common core plugins

c.f. https://github.com/fluent/fluentd/issues/407
Accept not a proc but a block as an argument
Merge pull request #414 from itiut/can-register-loop-conditions

Can register conditions in which the loop continues/exits
Merge pull request #424 from kiyoto/example_configs

example configs for common core plugins