Some code cleanup after bundling v8-profiler

- Moves C++ code under src folder
in order to follow node core convention.

- Removes preinstall directive in package.json

- Removes unnecessary v8-profiler files now
that it is being bundled

- Fixes https://github.com/c4milo/node-webkit-agent/issues/24#issuecomment-28551112

- Bumps version
Merge branch 'master' of github.com:c4milo/node-webkit-agent