Better error messages for the namespace argument

Work around when the first arg is -1

When seemingly valid arguments are given for non existent classes,
return a meaningful error message.
Bump version up to 2.3.3-SNAPSHOT.
fix(jar): Add directory entries to the jar file

According to the [jar file specification](http://docs.oracle.com/javase/7/docs/technotes/guides/jar/jar.html)

> For resource files with non-empty directory prefixes, mappings are also
> recorded at the directory level.  Only for classes with null package
> name, and resource files which reside in the root directory, will the
> mapping be recorded at the individual file level.

If needed, directory entries may be excluded using `:jar-exclusions`
regex like `#"^.*/$"`.
Merge branch 'jar-directory-entries' of https://github.com/dm3/leiningen
Reorder the skip/added file check.

Also document internals and decouple the skip/added file check.
Fix a bug where *cwd* wasn't honored for project parsing.
Described *1-*3,*e in repl-welcome

I have learned only by chance about the fact that REPL stores evaluation results in *1 - *3 and the last exception in *e. I am certainly not the only one unaware of this so it would be good to include it in the welcome message.

(For random visitors: they are defined in clojure's [`./src/clj/clojure/main.clj`](https://github.com/clojure/clojure/blob/master/src/clj/clojure/main.clj).)
Clean up helper docstrings.
Go from use->require.
Delete subdir directory.
Reenable java main run test.

Also more changes from use to require.
fix #1309 - lein.bat now honors HTTP_CLIENT env var
Merge pull request #1312 from kumarshantanu/master

fix #1309 - lein.bat now honors HTTP_CLIENT env var
Add ^:skip-aot as default for app template.

Elaborate more on when ^:skip-aot will disable compilation. Would be
great to cut out a lot of that documentation for 3.0.0.
Fix a bug where specified repl host was ignored.
Remove usage of soon-to-be legacy API in nrepl.
Allow default eval-in dispatch value to be changed with a defmethod.
Handle stdin for :eval-in :nrepl.
Slight clarification to checkout dependency usage
`lein install` may not be needed if `lein` can find the library in another
repository.