fixed out-of-sources build and tested it

Out-source-build failed:
```
../raid/internal.h:46:23: fatal error: ../config.h: No such file or directory
 #include "../config.h"
```
tested with:
```
mkdir build 
cd build
../configure
make
```
the fix might need more testing under Windows.

`.travis.yml` enables Travis testing, results for my fork here:
https://travis-ci.org/ottxor/snapraid