`dust doc` improvements

[heyLu]

dust doc exists now, thanks to @alekcz. Here are a few possible improvements to it. (Feel free to work on any of these, or add more, just say so in a comment.)

• show usage message if no argument is passed (currently an exception)
• load ns if symbol has an ns part, e.g. dust doc 'pixie.csp/put!' should work, even without -all
• fix duplicate results for -all (with pixie.csp/put! it displays the docs multiple times, with somewhat strange output)
• display signatures and examples as well
• dust doc should work outside of project directories (for the default namespaces)

[alekcz]

Strange output? What does the output look like?

[heyLu]

The docstring for the same function is repeated multiple times, but with invalid/strange symbols as the names, seemingly one for each namespace.

$ dust doc 'pixie.csp/put!' -all
  pixie.csp/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.


  pixie.uv/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.


  pixie.repl/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.


  pixie.streams/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.


  pixie.ffi-infer/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.


  pixie.io.common/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.


  pixie.io.tty/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.


  pixie.io.tcp/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.


  pixie.io.uv-common/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.


  pixie.io/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.


  pixie.io-blocking/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.


  pixie.fs/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.


  pixie.set/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.


  pixie.string/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.


  pixie.walk/pixie.csp/put!

    Puts the value into the channel, calling the optional callback when the operation has
   completed.

[alekcz]

@heyLu

dust doc  *
dust help  *
dust run *

This results in "deps" being sent as an argument. Any idea why this happens?