Implement the (and) function

The function takes at least two arguments, and turns it into a pythonic
and statement, which returns the last True-ish value, or False.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Implement the (or) function too

The (or) function is to be constructed similarly to (and), so refactor
the compile_and_operator function to handle or aswell.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Merge branch 'f/and-and-or' of git://github.com/algernon/hy into pr-79
style fixes