Use require_relative in tests.
Use require_relative for ohm/command.

Fixes:

```
$ # before
$ irb -r ./lib/ohm
`require':LoadError: cannot load such file -- ohm/command
>>

$ # after
$ irb -r ./lib/ohm
>>
```
Update redic version to 0.0.8.
Update msgpack version to 0.5.8. It has better support for Ruby 2.1.
Order dependencies by name.
Merge pull request #133 from frodsan/fix_requires

Use require_relative
Merge pull request #134 from frodsan/update_dependencies

Update dependencies