Bumps coverage ref

```
aa00d27 Merge pull request #30 from blazetopher/msgpk_lockdown
443500f Locks msgpack-python to 0.1.13
3403537 Merge pull request #29 from blazetopher/hdf_utils
112cb87 Adds hdf_utils package
262400f Merge pull request #27 from lukecampbell/threads_test
75de641 Increases the variance threshold for threads concurrency
```