Tests Fail on 0.5 / Some Improvements

[lruthotto]

Currently, the tests fail on 0.5.

Some obvious things to fix are:

• replace all RemoteRef{Channel{Any}}
• add MaxwellUtils to REQUIRE file
• add .travis.yml and appveyor.yml files
• add badges for tests and Coverage reports to README.md

While we're at it, we may want to talk about

• solveMaxFreq if MUMPS is used, the variable sym is not used.
• adding docstrings for types and constructors
• we could probably combine the first two functions in getSensTMatVec (the first one could be replaced by calling the second one and making the result real.