Added nightly building with travis
use the nightly build script for travis.

only deploy nightly builds if:
 - the build succeded
 - the branch is master
 - the job number is 1 or 5 (1 = linux executable compiled with clang and debuginfo or 5 = windows exe cross-compiled with dbginfo)
bundle data-repository just for the master, but still deploy otherwise

name the zip accordingly to the plattform (linux or windows)
Updated the nightly ftp server
Added sha512sum checksum and upload timeout of 30 minutes
Merge pull request #47 from inexor-game/fohlen/nightly



Add nightly builds

Did the thing!