Remove message size restriction

[LivInTheLookingGlass]

There are multiple proposals on the table for how to do this. I will summarize the two in comments below. connects to #69

[LivInTheLookingGlass]

Proposal 1:

Change how the initial message header is constructed. To get the initial header, the following script would work:

def how_many_bytes(i):
    num_bytes = 0
    while i:
        i >>= 8
        num_bytes += 1
    return num_bytes

def pack_header(i):
    lengths = [i]
    string = b""
    while i != 1 or lengths == [1]:
        i = how_many_bytes(lengths[-1])
        lengths.append(i)
    for index, length in enumerate(lengths[:-1]):
        print("Packing %i into %i bytes" % (length, lengths[index + 1]))
        string = pack_value(lengths[index + 1], length) + string
    return b'\x01' + string

This expands the possible message length to infinite scale. This proposal assumes that all headers are structured this way, including the packet separators.

[LivInTheLookingGlass]

Proposal 2:

1. Keep the 4GiB message limit
2. Add a continuation flag, which, if at the beginning of a message, specifies a message ID that it is extending, or if at the end of a message, specifies the message that will continue it
3. Have the .string call return a list of strings if this occurs

[LivInTheLookingGlass]

Issues #82, #83, #93, and #100 likely make this problem more difficult