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
Merge pull request #12 from linquize/msvc

Use _putenv_s instead of setenv on MSVC
Add copyright header in cangjieerrors.h
Change function return type to void to fix warning
Merge pull request #16 from linquize/no-return-value

Change function return type to void to fix warning
Merge pull request #15 from linquize/error-header-copyright

Add copyright header in cangjieerrors.h