patch tests to work with G::L::D v0.090 or earlier

The particular error message "Mandatory parameter '...' missing" has
changed in Getopt::Long::Descriptive between versions 0.090 and 0.091.
This commit patches MooseX::App's tests to allow for both versions of
the error message, allowing installs on platforms with a version of
G::L::D inferior to 0.091. Note that MooseX::App does not depend on
G::L::D directly.
Merge pull request #9 from ebaudrez/gld91_alt

patch tests to work with G::L::D v0.090 or earlier [ Alternative to previous pull request ]