structure: add constructor to provide a more advanced functions around
structs
field: add IsEmbedded and fix doc about Value()
field: add tests for fields, WIP
more tests, additional methods for fields
field: cover all cases for fields
field: add a method to get nested fields back
struct: increase coverage back to %100
structure: more improvements
structure: improve examples
Readme: small typo
Merge pull request #11 from fatih/struct

struct and field: two new types for a more advanced struct controlling