Fix metadata field rendering and log off-by-one error

[kyle-sammons]

Summary

When initially converting from the Grafana DataFrame to a normal log object, we were being a bit lazy and just using the _source object. That resulted in us not having access to metadata fields (such as _id, _timesinceepoch, etc). This PR properly implements the DataFrame -> Log conversion giving us back access to the metadata fields.

Resolves: #50

We also were running into an issue that was caused by forgetting that the row index in the table and the index of the log we're rendering are going to be off by one due to the table header. This manifested as a search with one log not displaying anything.
Resolves: #49

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

The following point can be removed after setting up CI (such as Travis) with coverage reports (such as Codecov)

• I've written tests to cover the new code and functionality included in this PR.

The following point can be removed after setting up a CLA reporting tool such as cla-assistant.io

• I've read, agree to, and signed the Contributor License Agreement (CLA).