Rewrite README, now with Markdown

I would have preferred a plain text summary with full information in the
man pages but that doesn't work well on GitHub so there has to be a bit
of duplication here.

README.md

@@ -0,0 +1,102 @@
+trickle & tritty
+================
+
+Slow pipe and terminal.
+
+ * Website: https://github.com/sjmulder/trickle
+ * Video: https://asciinema.org/a/143994
+
+trickle
+-------
+
+**trickle** [**-b** *bitrate*]
+
+**trickle** is used as part of a shell pipeline and has very low throughput,
+hence the name: data trickles through the pipe. By default, it passes on 600
+bits per second, but this can be configured:
+
+**-b** *bitrate*
+
+(For "baud", bits per second.) Must be a number in range 50-57600. A decimal
+separator and decimal 'k' suffix can be used.
+
+tritty
+------
+
+**tritty** [**-b** *bitrate*] [*command* ...]
+
+**tritty** ("trickle tty") spawns an interactive subterminal with very low
+throughput. It simulates the experience of using a terminal over a slow
+connection.
+
+By default, it runs at 600 bits per second (full duplex) but this can be
+configured:
+
+**-b** *bitrate*
+
+(For "baud", bits per second.) Must be a number in range 50-57600. A decimal
+separator and decimal 'k' suffix can be used.
+
+*command*
+
+Will be executed inside the virtual terminal. It defaults to the *SHELL*
+environment variable, or */bin/sh* if unset.
+
+Note that by only limiting throughput the serial device experience is not
+accurately simulated. In particular, the baud rate attribute on the virtual
+terminal is not set. Software may use this attribute to adjust their output.
+
+Use stty(1) from within a tritty session to adjust the baud rate attribute of
+the terminal as shown in the examples below. The original settings will be
+restored on exit.
+
+Examples
+--------
+
+Print *README* to the terminal at 600 baud:
+
+    $ trickle <README
+
+List files at 2600 baud:
+
+    $ ls | trickle -b2600
+
+List files at 57600 baud:
+
+    $ ls | trickle -b57.6k
+
+Browse the web with a 14400 baud terminal:
+
+    $ tritty -b14.4 elinks news.ycombinator.com
+
+Run the default shell at 2600 baud:
+
+    $ tritty -b2600   # now in the tritty session
+    $ man man
+      ...
+    $ exit
+    exit
+    $                 # back to regular terminal
+
+Run the default shell at 300 baud, also setting the terminal baud rate
+attribute:
+
+    $ tritty -b300
+    $ sty 300
+       ...
+    $ exit
+
+Building
+--------
+
+Should work on most Unix-like systems, perhaps with some tweaks. Tested on
+FreeBSD, macOS, Linux and Linux with musl.
+
+After tweaking the Makefile if desired:
+
+    make
+
+Author
+------
+
+By Sijmen J. Mulder (<ik@sjmulder.nl>)

trickle.1

@@ -26,10 +26,10 @@ suffix can be used.
 .El
 .Sh EXAMPLES
 Print
-.Li README
+.Li README.md
 to the terminal at 600 baud:
 .Pp
-.Dl $ trickle <README
+.Dl $ trickle <README.md
 .Pp
 List files at 2600 baud:
 .Pp