Version 0.8.0

Version 0.8.0

Changelog:

NMEA:
- benchmark for to_string(sentence) added.
- changed signature of nmea::make_sentence to make it more robust.
- serialization of sentences changed, gains performance by about 7 percent on average.

AIS:
- message 12 added.
- message 13 added.
- message 14 added.
- added missed function ship_name to message 19
- fix for the static initialization order issue from #8 for encode/decode of sixbit ascii.
- introduce rate of turn for messages 01/02/03

Tests:
_ bug fix: unit tests double comparison
_ bug fix: unit tests to compare coordinates as double

Misc:
- General: class data members named consistently.
- Examples: added example on using the library as git submodule.
- Examples: simple renaming.

Utils:
- added member function has_value to optional.
- bitset update to e865429e8a6c17366105e985fd037e42261a1af9.
- bug fix: bitset size is not extended properly

Doc:
- listed all supported compilers.
- minor cleanup for geo/cpa
- minor update, tested compilers.
- upgrade of the documentation generated by doxygen.

Build:
- benchmark updated to version 1.2.0
- build options for tests, tools and examples. Default values: ON.
- cmake cleanup and packaging
- compiler warnings extended, code refactoring according to findings.
- config for Clang-4.0 added.
- config for GCC-7 added.
- config for GCC-8 added.
- disable warning: shadow
- executing tests only if not disabled.
- fixed issues regarding Qt and CMake 3.11 features
- local installation directory specified.
- minor cleanup of CMakeLists.txt
- more precise cmake module path.
- target cppcheck now with more accurate include paths.
- test sources excluded from static analysis with cppcheck.

CI:
- disable clang-3.8 build on travis-ci
- update to cmake 3.11.4