Code coverage shows test folder and not app

The whitelisting of the code coverage was set to only show the coverage of
the test folder itself; which unsurpisingly was almost 100%. By changing the
whitelist to point to the app folder in the root of the project we get an
accurate representation of the code coverage.

After running the unit tests one can see the code coverage in the
build/coverage folder; by opening the index.html you can browse through all
files and determine what needs to be covered.
Remove superfluous and misleading echo's

In the each call to render seems to be prefixed with the echo keyword
but the render method does not return data; it adds the rendered output
to the view cache / output buffer so that it can be echo'd later
by Slim itself.

In this commit I remove all superfluous echo's since it may mislead
people into thinking that the echo's actually have a function and use
it to circumvent the view mechanism of Slim or have unpredictable bugs.
Merge branch 'pr115'
Merge branch 'remove-echos-before-renders' of github.com:mvriel/joindin-web2 into pr116
Merge branch 'pr116'