evolve_to_time: fix syntax error + implicit func

The function check_CFL is declared in a module, so it needs to be imported explicitly.
Merge pull request #5 from certik/syntax_fix

Syntax fix
Add CMake build system
Merge pull request #6 from certik/cmake2

Add CMake build system
Limiters should be integers

This fixes a compiler warning as well.
Merge pull request #7 from certik/limiter_fix

Limiters should be integers
Use 'dp' from precision_module everywhere

One should not use "kind=8" in modern Fortran, but rather have it as a
parameter declared at one place.
Travis-CI: Add initial .travis.yml

Once this basic setup works, we'll greatly expand it to also test Python
wrappers and various combination of configuration options.
Merge pull request #11 from certik/travis

Travis-CI: Add initial .travis.yml
Merge remote-tracking branch 'certik/dp_fix' into 1d-f90-conversion

Conflicts:
	src/clawdata_module.f90
Add utils.f90 and use stop_error()

The main problem is, that we need to test in our test suite that the library
works. If the library exits using:

    stop "some error message"

Then the main program will still exit with a zero exit code, so our test suite
passes... To fix this, one should use the "stop_error" subroutine:

    call stop_error("some error message")

That subroutine prints the message and calls "stop 1", which actually returns
a non-zero exit code and our test suite will fail.

Note that after this patch, our test will fail with a non-zero exit code and
Travis test will thus fail.
Travis: setup input file for our test
Travis: install classic in the "install" section
Travis: install clawpack (needed for tests)
Merge pull request #13 from certik/stop_error

Add utils.f90 and use stop_error()
Travis: fix the path
Merge pull request #15 from certik/fix_tests

Travis: setup input file for our test
Fix a NaN problem

Something fishy is going on with the association, it needs to be investigated
further. After this patch I am not getting any NaN.
Merge pull request #17 from certik/nan_fix

Fix a NaN problem
Update Makefile to run with new modules