Include dwmipcpp as a library in cmake and config files, so it can be built
automatically. The configuration of dwmicpp was added to match that of i3 and
bspwm to maintain the same cmake workflow and style.
* Clean up CMake logic
- removed logic to find CppUnit (no longer used)
- removed "dirs" variable used to pass include directories
- removed add_library function (no longer used)
- removed make_executable function
* only used in 2 places (polybar and polybar-msg)
* it was more general than needed, logic is simpler without it
- split polybar into static library and executable
* this allows linking unit tests to the library
* rename library
* add coverage build
- Added a CMake build type "Coverage" that builds C and C++
code with the "--coverage" flag (recognized by both GCC and Clang)
- removed "-Wno-missing-field-initializers" from test flags,
since it didn't seem to be needed any more
- removed logic from tests/CMakeLists to disable "-Werror" and "-pedantic-errors"
since there didn't seem to be any warnings during the build
* fix whitespace
* update travis
* remove O2 from defalt flags
* allow tests to be built by default make target
* disable Werror for debug builds
