Added Windows CI support with appveyor

Added support for http://www.appveyor.com/ (login via github account).

This will build the project and run the unit tests on Windows as well.
Possible to add a badge like with Travis in the README.md as well.
Merge pull request #205 from JoakimSoderberg/appveyor

Added Windows CI support with appveyor
Add AppVeyor badge to README.rst
Update CHANGES for 2.7
jansson 2.7
Don't use the nonstandard __FUNCTION__ macro
Use expr instead of $((...)) in shell scripts

For Solaris 10 compatibility.
Fix static CRT selection.
Fix CFLAGS for static-CRT build.

Setting the variables to only "/MT(d)" resets all other flags to their defaults, so the debug build used release flags.
Merge pull request #206 from chrullrich/fix-win-build

Fix CMake configuration for Windows build
README: Documentation is hosted at RTD
Warnings - use size_t where appropriate to prevent warning when compilation is targeting 64 bit
Merge pull request #208 from skeid21/master

Fix warnings on LLVM 6.0 targetion iOS arm64.
Include jansson_config.h with quotes

Fixes #209.