* add weighted_mean::sum_of_weights_squared
* sum of default constructed mean and weighted_mean is now equal to default constructed object
* thread-safe returns a reference to self in operators just like the other accumulators
- CMake: make compile-fail tests fail for the right reasons not because of missing headers
- CMake: run check_odr_test.py
- B2: actually run check_odr_test.py and check_build_system.py
* rename link test to odr test and check odr test completeness
* added convenience header for algorithm
* added minimal docs for axis.hpp, accumulators.hpp, algorithm.hpp
* temporarily remove display.hpp (will return in another patch)
* introduce offset for faster linearization of non-growing axes
* added traits::is_inclusive and constexpr bool inclusive() methods for builtin axes
* bug fixes for fill method when weight array is used with non-inclusive axis and when growing axes are used
* bug fix of axis::options::test(...)
* coverage tested with gcc-8, updated CONTRIBUTING.md with coverage info
- Tests and benchmarks now only include the headers they really need.
- Warnings turned off for tests that compile with external boost libs that are not warning free
* provide unsafe access to buffer
* factored mp_int out into separate header and renamed to large_int
* refined adding behavior
* more warnings and comeback of coverage variant
* better coverage reporting
- new thread-safe accumulators for arithmetic types
- storages have a new flag `has_threading_support` to indicate support for parallel cell access
- histogram automatically synchronises growing axes and storage if necessary
* fixes broken msvc build
* smaller xml files for testing serialization
* fixing many warnings on msvc
* bug-fixes to mp_int regarding operators and new tests to check their behavior
* don't expect iterable histogram::at to have size method
* build benchmarks in release mode
* test everything by default when b2 is run on project directory
* more test coverage
* Travis uses b2 and codecov now
* replacing boost::multiprecision with custom implementation to avoid the dependency
* improved axis implementation: `update` is now a normal method
* introduced use_default tag type to set defaults
* whitespace fixes and doc update
