Merge pull request #57 from matthewp/slice

Added a macro for slice.
Merge branch 'matthewp-ternary'

Conflicts:
	include/macros.sibilant
recompile recent changes with `sibilant src/* -o lib`
add contributors to package.json and bump version
update the shortlink to macros, since the url was incorrect.
test *this* sibilant, not the system sibilant.

it should work to run on a new machine with nothing but node:

> git clone https://github.com/jbr/sibilant.git
> cd sibilant
> bin/sibilant -x test/test.sibilant
add travis to readme
nonzero exit if there are any failing tests.  this is necessary for travis.
travis test on more node versions
add test script to package definition.  this enables `npm test` — in theory travis will use this.
add assert-throws and assert-translation-error
use assert-translation-error instead of assert-translation when what we're really asserting is that it threw an error mid-translation
Don't double-wrap errors.  The throw macro already makes a new Error.
fix setf semicolons.
recompile with serf semicolons, revealing duplicated semicolons all over the place.  failing tests needed.
semicolons after if statements are totally unnecessary
correct the tests to reflect that we don't want semicolons after blocks (specifically if / else blocks)
remove semicolons after if blocks made by the (when …) macro
Allow (if-else…) to handle an odd number of arguments.

Closes #61
rebuild without post-block semis