Support "omitempty" on form tag

[michael2m]

Support form:"foo,omitempty" to skip default values from encoding/decoding. This aligns e.g. with JSON encoding/decoding behavior.

[deankarn]

Just to confirm you mean for the encoder portion?

great idea for an enhancement :) I'll look into it

[deankarn]

@michael2m this feature has been added in release 3.0.0