v0.3

This release mainly adds image I/O support for the TIFF format, making use of libtiff; but it also contains various other changes and bug fixes.

Changes include, but are not limited to:

• Support for I/O of images in TIFF format. (Not all possible TIFF images may be supported, due to the complexity of both the format and the libtiff library.)
• Add basic 1-D convolution functionality, in x & y-direction, using 1-D kernels.
• Add functions for view creation on DynImages/DynImageViews.
• Some header reorganization inside selene/img_io/.
• Use std::variant for submitting format specific options to write_image(); this is an API breaking change.
• Each message in an sln::MessageLog instance now carries the type of the message; this is an API breaking change.
• Add seek_end() function to I/O classes in selene/base/io/.
• Memory[Reader|Writer] now take a single [Mutable|Constant]MemoryRegion parameter, instead of two arguments. This is an API breaking change.
• Warning free builds with -Wconversion enabled (GCC & Clang).
• Use library instead of Boost.Filesystem for tests & examples, where available.
• Use CMake-generated export macros to enable keeping symbols of public API functions visible.
• Add CMake options to disable optional external dependencies.
• Add CMake option to specify symbol visibility.
• Add easy_build.sh script, to provide a proof-of-concept for building the library on older (Ubuntu) Linux systems.
• Improvements to the CMake output to the user.
• Improvements to the documentation on GitHub.
• Improvements to the documentation built by Doxygen.
• Fix test failures when building without libjpeg/libpng/libtiff.
• Fix image view type alias declarations.
• Fix correct stride adjustment in sln::ImageView constructor.