Add explicity for EventStream
 * show it explicity by NotImplementedError that EventStream is abstract class
 * add comments to describe difference between ArrayEventStream and MultiEventStream
 * remove comment-outed methods of ArrayEventStream to break interoperability of EventStream
 * remove comment-outed IoEventStream:
   * that is not implemented and is not going to be implemented
   * that is danger because it require io-stream to be opened until the EventStream is destructed
Fix broken badge URL
Add apache_error format to parse Apache error logs
Merge pull request #396 from fluent/add-apache-error-log-format

Add apache_error format to parse Apache error logs
Merge pull request #395 from camelmasa/fix-broken-badge

Fix broken Code Climate badge URL
Update README.md
Merge pull request #393 from tagomoris/fix_event_stream_collections

Add explicity for EventStream
InputTestDriver sleeps exactly until input loop emits all the test data

In order to avoid sleeping long, specify expected emits and then
InputTestDriver continuously sleeps very short so that input loop will emit all the test data.
Use SVG badge for Travis CI
Can specify only the length of expected emits and assert emits after InputTestDriver#run
Update Fluentd's description
Merge pull request #398 from dlackty/patch-1

Use SVG badge for Travis CI
Initialize `@content_type` per request not per connection
Change variable name

t0         ->
started_at
Add a comment about expected_emits_length
Merge pull request #397 from itiut/avoid-long-sleep

InputTestDriver sleeps exactly until input loop emits all the test data
Use expected_emits_length instead of sleep in in_object_space test
Add me to AUTHORS ;)
Add base test for SystemConfig. ref #403
Fix TextParser to add estimate_current_event
 * to set estimate_current_event on child parser instance, between initialize and configure
   * external code cannot set it before @parser.confgure()