Update project version and dependencies

Also changes to use dev-resources instead of test-resources, to match lein2
conventions.
Ensure propagation of metadata on stevedore forms

We correctly propagate :line metadata, and add :file metadata, to each stevedore source form
and use it in exceptions.  Removes use of slingshot and forces clojure 1.4+.
Add a marker to messages for script exit status

In order to allow grep'ing for status messages, a prefix is added to each
message. By default, prefix script exit status messages by '#> '.  The prefix
may be altered by binding pallet.stevedore.common/*status-marker*.
Add source form location in script comments

When generating script, insert the file and line of the source forms that
generate the script.  The file and line are inserted as comments on the line
preceding the generated code.  This is a convenient format that allows script
lines to be easily used in continuation lines, when chaining commands together
for instance.

Introduces pallet.stevedore/fragment, which is similar to p.s/script, except
that it disables source comments and ensures pipelines are kept on a single
line.  This is required in some expansion contexts.

The pallet.stevedore/with-source-line-comments macro can also be used to control
the output of source comments when using p.stevedore/script.