Upgrade prismatic dependencies to 0.2.0

This commit upgrades trapperkeeper to use prismatic plumbing/graph
version 0.2.0.  The main changes in this version are that they have
ported the fnk input/output schemas to use their schema library rather
than the more custom solution that they were using before.

plumbing 0.2.0 also includes a patch that we submitted to them to
make their graph compilation / instantiation code throw ExceptionInfo
exceptions with more useful information about the compilation error;
this allows us to give slightly better error messages when a user
has an error in their service definition.