* Ion and Philipp's table retries
* Refactor the retry struct:
- Rename it from retry_struct to retry_info
- Retry information contains the failure callback, not the retry callback
- All functions take in retry information as an arg instead of its expanded fields
* Rename cb -> callback
* Remove prints
* Fix compiler warnings
* Change some CHECKs to greatest ASSERTs
* Key outstanding callbacks hash table with timer ID instead of callback data pointer
* Use the new retry API for table commands
* Memory cleanup in plasma unit tests
* fix Robert's comments
* add valgrind for common
* Remove hiredis submodule.
* Squashed 'src/common/thirdparty/hiredis/' content from commit acd1966
git-subtree-dir: src/common/thirdparty/hiredis
git-subtree-split: acd1966bf7f5e1be74b426272635c672def78779
* Make Plasma tests pass.
* Make Photon tests pass.
* Compile and test with Travis.
* Deactive fetch test so that the tests pass.
