gitignore: ignore bin directory in the root folder
gitignore: ignore bin directory in the root folder

It pops up when there's no Eclipse classpath set and eclipse tries to
compile the project.

Signed-off-by: Daniel Halperin <1a02732a15f637c31107256cbee5819e36aa7c67@cs.washington.edu>

uwescience/myria,jamesmarva/myria,uwescience/myria,uwescience/myria,jamesmarva/myria,jamesmarva/myria,bsalimi/myria,bsalimi/myria,bsalimi/myria