Added delete() function.

  This deletes the current/named message.
  Added new primitive: sendmail_path()

  This will get/set the sendmail path, for sending mails.

  This updates issue #4.
  Sending mail works.

  This is still not very neat/tidy, but an outgoign mail was
 successfully delivered.

  This updates issue #4.
Add stat call for the date header
  Determine which headers to display via lua.

  The table "headers", set by lua, will now control what headers
 we display when reading a message.

  See:  http://lumail.org/lua/headers.html

  Closes #6.
Merge pull request #12 from 7histle/master

Add stat call for the date header.
  New version.

  Since the display of message-headers is now handled and we can
 send an email (albeit in an ugly fashion) we're OK to bump the
 version number.
  Update to reflect status:

  * We can delete messages.
  * We can compose mails, albeit in a basic fashion.
  We used "headers" rather than "message_headers".

  But otherwise this is implemented now.
  Pass keypresses through key_name().

  ncurses provides the `key_name` function to convert between
 a char and a string representing the key, taking into account
 ctrl- + meta-.

  This means Ctrl-r is now reported as ^R, and can be both bound
 and looked up as such.
  Reworded the coding section.

  We don't need to refer to cmail, and we should point out that
 lumail.lua is not executed any more.   (Not true at the moment,
 but will be very very shortly.)
  We don't load ./lumail.lua now.

  This is a security risk if you install system-wide.

  Instead please use one/both of:

* `/etc/lumail.lua`.
* `~/.lumail/config.lua`.

  Or run:

`lumail --rcfile ./lumail.lua`.
  Abort if we can't load an init-file.

  This avoids a segfault when displaying, or processing keystrokes.
  Updated comments and indentation.

  The indentation is now consistent, and the comments explain
 the exit() choice.