Adjust names to conform to style guidelines.

# Adjust Names per Style Guidelines

Running the code through `golint` kicks up a little dust; this resolves the majority of complaints.

I left the following three items unaddressed for now.

```
canaryd.go:19:6: exported type Config should have comment or be unexported
canaryd.go:25:6: exported type Check should have comment or be unexported
canaryd.go:30:6: exported type Measurement should have comment or be unexported
```