Support test arguments in reporttests.jl

[omus]

Changes include:

• Support passing in test arguments to reporttests.jl
• Make reporttests.jl executable to actually use the hash-bang
• Support specifying a log filename as an option to reporttests.jl
• Utilize the internal runner code instead of duplicating code
• Support code coverage when running reporttests.jl (need to call julia --code-coverage reporttests.jl ...)
• Return the exit code of the subprocess
• Add tests for reporttests.jl

[oxinabox]

Once these comments are addressed to your statisfaction, feel free to merge