Log cleanliness

Provides the ability to exclude messages based on simple filters.

Add Log method

This release adds a Log method that can be used to log data given a level passed in as an argument. Useful for dynamic leveling decisions.

Taming panics and mutexes

This release removes a source of potential panic calls from the logging path where either a non-string value was passed as a key or an odd number of arguments were passed to a log method.

Additionally, a bug related to mutex copying has been fixed.

Colors, Sinks, and Interceptors Oh My!

• Now with color support!
• Now supports a mechanism to treat logger trees with different levels!

Now with Context!

Merge pull request #42 from hashicorp/f-context

{From,With}Context for storing a logger in a context.Context

v0.8.0: Merge pull request #37 from hashicorp/svh/f-level-writer

Rename `NewLevelWriter` to `NewLeveledWriter`

Feels like it's about 1.0

It's in production but unsure what should be in there for it to be 1.0, so 0.7 feels about right.