Update to 1.25

Upstream changes:
Release 1.25 - 11 May 2017
- Fix C code to work with MSVC (Marc-Philip) (github 177).
- Fix cover command using Module::Build on Win32 (sago35) (github 160).
- Add file and line info to keep ops unique (Niko Tyni) (github 143).
- Report coverage for all declarations (Heinz Knutzen) (github 166).
- Fix spelling mistakes (Gregor Herrmann) (github 171).
- Fix condition coverage for complex conditions (Heinz Knutzen) (github 165).
- Use JSON::MaybeXS for sppen and flexibility (Olivier Mengu矇) (github 139).
- Add CONTRIBUTING file (Gabor Szab籀) (github 100).

(wen)