add a test page with some keys and PGP blobs

this makes testing the work-flow more easy. For now you can serve this
by running `python -m SimpleHTTPServer` in the `spec/` directory. A
serve task to grunt might be added, later.
make testing in firefox more easy

There is now a test profile that can be used for development. There is one
key (public and private) preconfigured and the test page is also added by
default. Also the test page is added as a bookmark to open it easily.
cleanup readme

use correct citation (intepret this as code, not as citation)
add grunt-contrib-connect as a simple http server

this is great for running a local server to speed up development.
remove --keepalive option

this can be achieved more elegantly by adding keepalive as a "sub-task"
add new unknown key

the old one seems to be broken somehow, at least, it triggers an exception.
Leaving the "broken" one in, since it’s a good test.
Merge branch 'feature/tests' into feature/verify_signatures
add support for sandboxed verification in a popup

for even more security, provide a popup-version of signature verification.