Merge pull request #10 from linquize/msvc

Use _putenv instead of setenv on MSVC
ci: Add a Travis configuration

This fixes #5.
Merge pull request #11 from Cangjians/travis

ci: Add a Travis configuration
Use _putenv_s instead of setenv on MSVC

This fixes commit 9194bc9174f98a11458d138cda7794550e262418