numerous small bugfixes
Merge pull request #8 from ericbmerritt/master

bug fixes and cleanup to the vagrant file.
Add support for {vm_args,_} argument in config
Merge pull request #10 from lafka/lafka-vmargs-opt

Add support for {vm_args,_} argument in config
Fix call to rlx_state:vm_args/2
Merge pull request #11 from essen/fix_rlx_state_call

Fix call to rlx_state:vm_args/2
Check presence of each beam listed in .app

This allow to build riak, because one of riak deps (node_package) have stuff
in priv/ and valid node_package.app, but no one .beam files.