web/app: configure path to page templates

Express searches page templates in `$(pwd)/view` by default.
That obviously does not work when the server is started via

    node web/app

In this commit, the express app is configured with a views path
resolved using `__dirname`, which makes it independent on the current
working directory.

/to @ritch please review

This patch resolved the regression introduced by #10 as described in #12.