Run httpbin locally for the tests in the CI builds

Run httpbin (either directly or inside a container) and set
WX_TEST_WEBREQUEST_URL to point to localhost.

Note that it is important _not_ to have a trailing slash in the root
URL, otherwise WebRequest::Auth::Digest test would fail.

build/tools/travis-ci.sh

@@ -12,6 +12,16 @@ wxBUILD_ARGS="-j$wxPROC_COUNT"
 # messages from WebKit tests that we're not interested in.
 export NO_AT_BRIDGE=1
 
+launch_httpbin() {
+    echo 'travis_fold:start:httpbin'
+    echo 'Running httpbin container...'
+    docker pull kennethreitz/httpbin
+    docker run -d -p 80:80 kennethreitz/httpbin
+    WX_TEST_WEBREQUEST_URL="http://localhost"
+    export WX_TEST_WEBREQUEST_URL
+    echo 'travis_fold:end:httpbin'
+}
+
 case $wxTOOLSET in
     cmake)
         if [ -z $wxCMAKE_TESTS ]; then wxCMAKE_TESTS=CONSOLE_ONLY; fi
@@ -42,6 +52,8 @@ case $wxTOOLSET in
         echo 'travis_fold:end:install'
 
         if [ "$wxCMAKE_TESTS" != "OFF" ]; then
+            launch_httpbin
+
             echo 'travis_fold:start:testing'
             echo 'Testing...'
             ctest -V -C Debug -E "test_drawing" --output-on-failure --interactive-debug-mode 0 .
@@ -124,6 +136,8 @@ case $wxTOOLSET in
             exit 0
         fi
 
+        launch_httpbin
+
         echo 'travis_fold:start:testing'
         echo 'Testing...'
         pushd tests