Added dnserver description to README.md
Use JLine 2 to let dnserver read unbuffered input

Defined a function read-sql-statement to read characters from standard
input, until a semicolon or EOF character is read. The sequence is then
output.

With this method, characters are not visible if the user types it in
from the command line, but since this is meant to be executed by
dnclient over ssh, it shouldn't be an issue. However when experimenting
with clj-ssh to execute dnserver remotely over SSH, there is an
exception output by dnserver if clj-ssh's ssh command is called with :in
set to a character sequence containing no trailing semicolon (e.g.
"1234"). If :in is set to a string containing a trailing semicolon (e.g.
"1234;"), then clj-ssh returns the expected return value printed from
read-sql-statement.

I experimented with using clj-ssh to call "md5sum -" remotely with :in
being set to "1234" and it worked fine, so currently the EOF is not
detected properly by dnserver.