Inherit key coercions

[Erol]

This fixes #255.

[dblock]

Any better way to do this than via an instance_variable_set? Maybe expose a property?

Looks good otherwise, needs a CHANGELOG entry please.

[Erol]

How about this? I created a protected key_coercions= property setter to setup up inherited coercions.

On another note, I noticed that most properties were defined as:

def strict_value_coercions
  @strict_value_coercions || {}
end

And then conditionally initialized and used:

if options[:strict]
  (@strict_value_coercions ||= {})[from] = into
else
  ...
end

How about if we redefine them as:

def strict_value_coercions
  @strict_value_coercions ||= {}
end

And use them immediately, without worrying about initialization? It looks cleaner:

if options[:strict]
  strict_value_coercions[from] = into
else
  ...
end

Your thoughts?

[dblock]

This is perfect, merged via a493872.

Your proposal seems sensible, feel free to PR further.