Point amber to files path

[baldurmen]

While trying to run amber with bundle exec amber to keep gem files in a specific directory, I found that:

• I could not get bundle exec amber to work outside of the amber directory
• amber refused to server anything since I was not in the directory where the website files were (Could not find amber/config.rb in the directory tree. Run amber from inside an amber website directory)

I think this could be solved if you could run something like amber server --path instead of needing to run amber in the website files working dir.

I ended up symlinking a bunch of stuff to make this work, which is not ideal.