adding appraisal library to allow testing of multiple rails versions
dont use appraisal for travis, use mutliple gemfiles instead
fix rails version incompatibilities for dummy app
change rails development dependency to >= 3.0.0, reduce travis build matrix
fix rails 3.0 incompatibility, reduce travis build matrix again
temporarily allow failures for rails 3.0 and 4.0
test show_exceptions middleware exception handling, run all tests twice with local and non-local requests
update gitignore