Guidelines on filing issues + release notes update.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=117220082

CONTRIBUTING.md

-# How to Contribute #
+# How to contribute #
 
 
-We'd love to hear your feedback. Please open new issues describing any bugs,
-feature requests or suggestions that you have.
+## Reporting issues ##
+
+We use the [GitHub issue tracker](https://github.com/google/ExoPlayer/issues)
+to track bugs, feature requests and questions.
+
+Before filing a new issue, please search the tracker to check if it's already
+covered by an existing report. Avoiding duplicates helps us maximize the time we
+can spend fixing bugs and adding new features.
+
+If you're filing a bug, be sure to provide enough information for us to
+efficiently diagnose and reproduce the problem.
+[Reporting an issue](https://google.github.io/ExoPlayer/2015/10/01/reporting-issues.html)
+gives some examples of what to include.
+
+## Pull requests ##
 
 
 We will also consider high quality pull requests. These should normally merge
 We will also consider high quality pull requests. These should normally merge
 into the [dev][] branch rather than master. To contribute in this way you must
 into the [dev][] branch rather than master. To contribute in this way you must
@@ -9,11 +22,10 @@ first submit a Contributor License Agreement, as described below.
 
 
 [dev]: https://github.com/google/ExoPlayer/tree/dev
 [dev]: https://github.com/google/ExoPlayer/tree/dev
 
 
-
-## Contributor License Agreement ##
+## Contributor license agreement ##
 
 
 Contributions to any Google project must be accompanied by a Contributor
 Contributions to any Google project must be accompanied by a Contributor
-License Agreement.  This is not a copyright **assignment**, it simply gives
+License Agreement. This is not a copyright **assignment**, it simply gives
 Google permission to use and redistribute your contributions as part of the
 Google permission to use and redistribute your contributions as part of the
 project.
 project.
 
 

RELEASENOTES.md

 # Release notes #
 # Release notes #
 
 
+### r1.5.5 ###
+
+* DASH: Enable MP4 embedded WebVTT playback (#1185)
+* HLS: Fix handling of extended ID3 tags in MPEG-TS (#1181)
+* MP3: Fix incorrect position calculation in VBRI header (#1197)
+* Fix issue seeking backward using SingleSampleSource (#1193)
+
 ### r1.5.4 ###
 ### r1.5.4 ###
 
 
 * HLS: Support for variant selection and WebVtt subtitles.
 * HLS: Support for variant selection and WebVtt subtitles.