Fix cp failures

[asymmetric]

• Fixes errors like: cp: ‘/tmp/build_53960f7b097c02e37827c199ce104686/bower.json’ and ‘./bower.json’ are the same file
• explicitly cds to the necessary directory, so that each function's body is self-descriptive
• avoids using cd -, because it makes it harder to know which dir you'll be jumping to (since it depends on the order of execution)

[gjaldon]

Thanks for the PR @asymmetric!