remove unused travis files

these have not been used for a while. .travis.yml and the files in opm-common/travis/ are in charge

travis/build-and-test-opm-core.sh

@@ -1,8 +0,0 @@
-#!/usr/bin/env bash
-set -e
-
-pushd . > /dev/null
-opm-core/travis/build-opm-core.sh
-cd opm-core/build
-ctest --output-on-failure
-popd > /dev/null

travis/build-opm-core.sh

@@ -1,10 +0,0 @@
-#!/usr/bin/env bash
-set -e
-
-pushd . > /dev/null
-cd opm-core
-mkdir build
-cd build
-cmake -D SUPERLU_ROOT=../../SuperLU ../
-make
-popd > /dev/null

travis/clone-and-build-dune-istl.sh

@@ -1,12 +0,0 @@
-#!/usr/bin/env bash
-set -e
-
-pushd . > /dev/null
-git clone https://github.com/dune-project/dune-istl.git
-cd dune-istl
-git checkout tags/v2.3.1
-mkdir build
-cd build
-cmake ../
-make
-popd > /dev/null

travis/clone-and-build-superlu.sh

@@ -1,11 +0,0 @@
-#!/usr/bin/env bash
-set -e
-
-pushd . > /dev/null
-git clone https://github.com/starseeker/SuperLU.git
-cd SuperLU
-mkdir build
-cd build
-cmake -D CMAKE_INSTALL_PREFIX=.. -D SUPERLU_BUILD_EXAMPLES=OFF -D SUPERLU_ENABLE_TESTING=OFF ../
-make install
-popd > /dev/null