rustpub 0.1.7

An implementation of the Activitypub types
Documentation
This is an in-progress implementation of activitypub types.  
It is still in the experimental phase and there will be breaking changes every update.

The `rustpub::simple` module contains a simplified activitypub type implementation.  
It has Object and Link types that have all of the properties of the base and child types combined into one type.  
The `rustpub::complex` module contains separate types for each activitypub type and uses traits to connect them.  
The `rustpub::complex` module is not yet usable.

## Activitypub Types Implementation
### Properties
- [x] actor
- [x] attachment
- [x] attributedTo
- [x] audience
- [x] bcc
- [x] bto
- [x] cc
- [x] context
- [x] current
- [x] first
- [x] generator
- [x] icon
- [x] id
- [x] image
- [x] inReplyTo
- [x] instrument
- [x] last
- [x] location
- [x] items
- [x] oneOf
- [x] anyOf
- [x] closed
- [x] origin
- [x] next
- [x] object
- [x] prev
- [x] preview
- [x] result
- [x] replies
- [x] tag
- [x] target
- [x] to
- [x] type
- [x] url
- [x] accuracy
- [x] altitude
- [x] content
- [x] name
- [x] duration
- [x] height
- [x] href
- [x] hreflang
- [x] partOf
- [x] latitude
- [x] longitude
- [x] mediaType
- [x] endTime
- [x] published
- [x] startTime
- [x] radius
- [x] rel
- [x] startIndex
- [x] summary
- [x] totalItems
- [x] units
- [x] updated
- [x] width
- [x] subject
- [x] relationship
- [x] describes
- [x] formerType
- [x] deleted
### Extented Properties
- [x] PublicKey
- [x] PublicKeyPem
- [x] PreferredUsername
- [x] Inbox
- [x] Outbox
- [x] Followers
- [x] Following