bower install self_signed_cert_in_chain

It finally worked for me. These are the steps I took:

1. Uninstall bower from npm npm uninstall bower or npm uninstall -g bower
2. Install bower-canary from npm npm install bower-canary or npm install -g bower-canary
3. Create .bowerrc in your project directory with the following content to turn off SSL:

{ "strict-ssl": false,  "https-proxy": "" }

4. Then try again bower install angular-bootstrap