Implement Basic Tipset about forest

[dutterbutter]

pub fn NewTipSet {
// The blocks must be distinct (different CIDs), have the same height, and same parent set

// Also sorts tickets from smallest to largest; sorted array so index 0 is the smallest ticket in tipset

// returns TipSet type
}

Will also need to implement fn for identifying and attaching unique tipSetKey

[dutterbutter]

Included:

tipset methods

• new() // builds a new TipSet from a collection of blocks
• at() // returns the i'th block in the tipset
• equals() // tests whether the tipset contains the same blocks as another

block methods

• cid() // returns the content id of this block
• decode_block() // decodes raw cbor bytes into a Block
• signature_data() // returns the block's bytes without the blocksig for signature creating and verification

tipsetkey methods

• new() // initialises a new tip_set_key
• new_from_unique() // initialises a set with CIDs that are expected to be unique
• equals() // checks whether the set contains exactly the same CIDs as another

ticket methods:

• sort_keys() // returns the canonical byte ordering of the ticket