Make us of idiomatic Maybe monad for Ruby

The gem andand provides an implementation of the Maybe monad in Ruby.
This way I was able to eliminate the helper method used to retrieve the
value of a multiple nested hash.

The previous implementation used exception handling for cases which are
not very exceptional, but rather to be expected. This should be avoided
anyway.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Colorize completeness metric detail view

I have defined a green and red color to illustrate whether a field has
been completed or not. This way the user gets a more visual idea of the
currently displayed results.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add some more table styling

Just added some more table styling, including bold font weight for the
field labels and text alignment.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>