Merge pull request #29 from metamatt/master

Correct docs for the callback.
appveyor: remove libusb installation stuff

Cargo-cult programming FTW!
weakref: fix deprecation warning after nan upgrade

The memory management of the `data` structure is now handled
internally by nan.
.travis: don't test node v0.9.x

Travis doesn't have it installed anymore so the builds fail.
appveyor: hopefully better appveyor file
README: add appveyor build badge
README: use SVG Travis badge
v0.3.2
package: update "nan" to v1.2.0
package: update "mocha" to v1.20.1
appveyor: more generic comment
v0.3.3
travis: test node v0.6
appveyor: attempt to test x86 and x64, Debug and Release configs
Revert "appveyor: attempt to test x86 and x64, Debug and Release configs"

This reverts commit 7c99cd620a5743d8b4d14ab49a44a065cc5a7792.