Markdown readme.md

Co-Authored-By: Petr Vaněk <arkamar@atlas.cz>

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Torrents added with previous versions of btpd will show up as "bad torrent entry"

Closes GH-26

Closes GH-32

Closes GH-34

Accept bencoded dictionaries whose keys are not in alphabetical order.

Closes GH-30
Closes GH-36

Accept .torrent files whose bencoded dictionaries are not in
alphabetical order.

This specifies the number of wanted peers to the tracker and is
configurable from the commandline flag "--numwant".

Closes GH-5

This adds a 'rate' command to modify the up and download
rates on the fly.

Closes GH-10

Patch submitted from Cesare Falco.

Closes GH-19

Added printf()-style '%' and '\' sequences for custom list formats.
Updated btcli manpage to reflect change and start -a.

Closes GH-8

Modified patch from savrus and nicm.
Allows adding multiple torrents from one 'btcli add' command.
Also made minor improvements to add code.

Closes GH-9

There was a warning at the end of addrinfo_td because it returns
a "void *" but had no return statement.  The fix was call pthread_exit().

Closes GH-7

There was a hard-coded 2MB file size limit on the .torrent files.
Set the limit to 0 so read_file() will use the actual file size.

Closes GH-14

Applied OpenBSD patches from Nicholas Marriott.
Closes GH-12

Lars Nooden originally put these together for OpenBSD.
They contain the same information from --help and the README.

With kqueue, a fdev may be in two active kevents.

'==' does work in some implementations though.

The timeouts for poll and epoll are given in milliseconds,
which caused busy looping in the event loop for timeouts
with less time remaining.

On some systems no extra flags or libs are needed.

The incorrect length caused problems on MacOs X.

There really should be a btter way to do this, but I can't
find it. :(

Log which peer contributed what to a piece. Do not try to download the
same piece from the same peers. Don't download at all from peers implicated
in 3 bad pieces. When a previously bad piece has been downloaded successfully
the bad peer(s) can be found and banned.

struct peer is now peer and meta_peer. meta_peer can be used as
a handle that won't be affected if a peer vanishes. The meta_peers
are kept in a hash table to enable fast lookup by peer id.