Add matchers.Format for matching common types

[chrislawlor]

Adds the match common formats feature from pact-python:

from pact import Format
Format().integer  # Matches if the value is an integer
Format().ip_address  # Matches if the value is a ip address

can be used in place of other matchers:

from pact import Like, Format
Like({
    'id': Format().integer, # integer
    'lastUpdated': Format().timestamp, # timestamp
    'location': { # dictionary
        'host': Format().ip_address # ip address
    }
})

Supported formats:

matcher	description
identifier	Match an ID (e.g. 42)
integer	Match all numbers that are integers (both ints and longs)
decimal	Match all real numbers (floating point and decimal)
hexadecimal	Match all hexadecimal encoded strings
date	Match string containing basic ISO8601 dates (e.g. 2016-01-01)
timestamp	Match a string containing an RFC3339 formatted timestapm (e.g. Mon, 31 Oct 2016 15:21:41 -0400)
time	Match string containing times in ISO date format (e.g. T22:44:30.652Z)
ip_address	Match string containing IP4 formatted address
ipv6_address	Match string containing IP6 formatted address
uuid	Match strings containing UUIDs