Tuned travis file

I changed a few things:
1. instead of checking with "--enable-debug" and "--enable-debug --enable-debug-glibcxx"
  I always use both.
2. I check with debug flags and serial compiler (before it was only debug+MPI)
3. I changed the order so that runs with manual is the first and runs
  with debug options are also made earlier. This is convenient since they
  take more time