Slicing a HyList makes the same kind of object again
Make empty macroexpansions do the right thing
Add a cons object and related mechanisms

Closes: #183
Reorganize documentation.
Add `items`, `values` and `keys` methods to HyDict

Useful for macros, for example:

    (defmacro defn-checked [n x b]
      `(defn ~n [(unquote-splice (.keys x))]
        (print "Expecting:" (unquote-splice (.values x))) ~b))

    (defn-checked hello {name str age int}
      (print "Hello" name "you are" age))

    (hello "Godzilla" 60)

    ;; Expecting: <type 'str'> <type 'int'>
    ;; Hello Godzilla you are 60
Add tests for HyDict methods
Add Brian McKenna to AUTHORS
Fix single spaces between methods in test_dict.py
Attempt to fix HyDict#items for Python 3

Looks like Python 3 changed `zip` to returning an iterable and not a
list. We should be good to just wrap the call in `list`.
Add integer-char? to core
Merge pull request #480 from agentultra/digit-char

Add integer-char? to core
README.md: Add Adderall to Hylarious Hacks

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
Fix unicode error #483
Merge master onto pr/473
Merge master onto pr/482
Update tutorial.

- Fix a couple of typos
- Use open() built-in instead of file()
- Update (for) and (with) examples
Move all badges to top of README.
Add new author
Merge master onto pr/486
Merge master onto pr/471

Conflicts:
	hy/core/language.hy