make iterators a bit friendlier to use

`first` now works on any IIterator, returning `-current`, and
`-iterator` is supported on IIterators as well to make the following
possible:

    (map inc (distinct [1 2 3 1 -1 10]))
Update README.md

Used Ubuntu package naming for guidance.
Merge pull request #118 from rcarmo/patch-1

Update README.md
added double support, confirming that strings are broken, WIP
Add links for library dependencies to README
VERY WIP, but fixes a stupid issue with ffi
removed debug stuff
Get the arg order right
Merge pull request #120 from pixie-lang/ffi-fixes

Ffi fixes
added buffer, and tests for ffi
fix a translation error
Merge pull request #122 from heyLu/coll-fixes

Make iterators a bit friendlier to use
Merge pull request #119 from benrhughes/master

Add links for library dependencies to README
implement numerator and denominator
fix math ffi on linux

On Linux, libm (and other libraries) are separate, so we have to use
different libraries. One of these is libm, which contains things like
`floor`, `atan2` and quite a few other things.

There should be symlinks from `libm` et al to `libSystem` on Mac [1], so
it should still work there.

[1]: http://www.finkproject.org/doc/porting/porting.en.html#basics.libraries
implement `int` and `float`
Merge pull request #121 from pixie-lang/ffi-improvements

Ffi improvements
Merge branch 'num-improvements'

Conflicts:
	pixie/stdlib.pxi
fixes getting io streams to work
move tests into a more sane directory structure. Now we don't have to load all tests just to run one ns