Freesasa

- Add `Result.write_pdb()`
- Add `Structre.addAtoms()`
- Fix bugs in `structureFromBioPDB()` where some options weren't handled properly
- Add chain-groups support to `structureArray()`.

- Fix error where CLI options weren't parsed properly on ARM processors.
- Fix error in man pages.

- Fix error where compiling without multithread support still set the default number of threads to 2.
- Fix issue when stripping quotes from atom names in CIF-files, which sometimes caused memory errors.

- Added changelog
- Can access absolute and relative SASA for individual residues through `Result.residueAreas()`
- Can set options and classifier for a `Structure` initiated without an input file for later
use in `Structure.addAtom()`
- Only build PyPi packages for Python 3.6+ (can still be built from source for older versions)

This version separates the Python bindings into a separate
[module](https://github.com/freesasa/freesasa-python).
To be able to release Windows binaries of the python module,
the code has been changed to be C89 compatible where necessary,
with a few macros to allow using `restrict` and `inline` when
compiled with a C99 compiler. There are no changes to the behavior
of the CLI or C API in this release.

- Relative SASA values are now calculated using the same reference
configurations as NACCESS. This means relative SASA values will
differ slightly from those of previous versions.
- Python bindings compatible with Python 3.
- Man page added
- Bugs fixed:
- CLI option `--separate-models` now outputs all models in PDB output.
- On some platforms compilation failed when libxml and/or json-c was
not present. Now fixed.
- Some memory allocations were not checked for failure in S&R
calculations. These are now properly checked, and done more
seldomly, which should improve performance slightly.
- Residue numbers now include the iCode field for insterted residues
- Compatibility with Microsoft C Compiler:
- No variable length arrays
- Some macros and keywords are redefined when necessary
- Lexer does not depend on header `unistd.h`
- GNU getline not used, replaced by fgets()