Merge pull request #2 from calfjohn/master

2 commits
Merge branch 'master' of github.com:fusijie/LudumDare31
Merge pull request #3 from calfjohn/master

One bullet is able to 'eat' the other bullet
Merge branch 'master' of github.com:fusijie/LudumDare31
Merge With Lijun.
make hero shoot.
Merge branch 'master' of github.com:fusijie/LudumDare31
fixed a bug in shoot bullets