DuckPAN/DDG: DuckPAN won't die when a module fails to load.

It's been a perennial problem for DuckPAN users to install all of the dependencies of each IA in the repo before they can even test anything. This patch prevents DuckPAN from exiting when it fails to load an IA. It goes on running, but it warns the user that some IAs didn't load (along with the errors that caused it). This is especially useful if the dependency is not only a Perl module (which is generally easy to install), but external libraries that may have different installation methods depending on the system (I'm looking at you GNU MPFR which needs `sudo apt-get install libmpfr-dev` on Ubuntu or `brew install mpfr` on OS X).

Here it is in action (ChineseZodiac missing a module):
![screen shot 2014-06-18 at 12 15 49 pm](https://cloud.githubusercontent.com/assets/81969/3316566/f516c8f0-f703-11e3-8585-41e5ad36badb.png)

Here it is displaying some other error:
![screen shot 2014-06-18 at 12 16 24 pm](https://cloud.githubusercontent.com/assets/81969/3316573/03a240b6-f704-11e3-9d81-16d72b84f831.png)

CC @moollaza @nilnilnil