Enhance Travis-CI to optionally compare Wok output

- Add file "test_site/wok_expected_output-test_site" which is the
  output of "wok -v" when run with current upstream master.
- Introduce new environment variable "CMP_OUTPUT" in .travis.yml.
- Enhance bin/site-tests such that if CMP_OUTPUT==true, it will run
  cmp on the wok_expected_output-$TEST_SITE file versus the output
  of the "wok -v" run.
- Goal of this enhancement is to support more robust testing of
  fixes for issues mythmon#144 and mythmon#145.

.travis.yml

@@ -3,10 +3,10 @@ python: ["2.7"]
 sudo: false
 
 env:
-  - PYTHON_TESTS=true TEST_SITE=false
-  - PYTHON_TESTS=false TEST_SITE=docs
-  - PYTHON_TESTS=false TEST_SITE=test_site
-  - PYTHON_TESTS=false TEST_SITE=OSULUG/OSULUG-website
+  - PYTHON_TESTS=true TEST_SITE=false CMP_OUTPUT=false
+  - PYTHON_TESTS=false TEST_SITE=docs CMP_OUTPUT=false
+  - PYTHON_TESTS=false TEST_SITE=test_site CMP_OUTPUT=true
+  - PYTHON_TESTS=false TEST_SITE=OSULUG/OSULUG-website CMP_OUTPUT=false
 
 script: 
   - bin/python-tests

bin/site-tests

@@ -26,5 +26,15 @@ fi
 echo "Testing site $TEST_SITE"
 
 cd $TEST_SITE
-wok -v
-exit $?
+EXPECTED_FILE=wok_expected_output-${TEST_SITE}
+OUTPUT_FILE=wok_output_travis-ci.${TEST_SITE}.`date +%Y%m%d-%H%M%S`.txt
+wok -v > $OUTPUT_FILE 2>&1
+rc=$?
+
+if [ -n "$CMP_OUTPUT"  -a  "$CMP_OUTPUT" = "true" ]; then
+    echo "Comparing output $EXPECTED_FILE $OUTPUT_FILE"
+    cmp $EXPECTED_FILE $OUTPUT_FILE
+    rc=$?
+fi
+
+exit $rc

test_site/wok_expected_output-test_site

@@ -0,0 +1,7 @@
+WARNING:root:Textile not enabled.
+WARNING:root:HTML rendering relies on the BeautifulSoup library.
+WARNING:root:To use compile_sass hook, you must install libsass-python package.
+WARNING:root:No parser found for html_renderer.html. Using default renderer.
+ERROR:root:It looks like the page "content/tests/dates1.mkd" is an orphan! This will probably cause problems.
+ERROR:root:It looks like the page "content/tests/dates2.mkd" is an orphan! This will probably cause problems.
+ERROR:root:It looks like the page "content/tests/dates3.mkd" is an orphan! This will probably cause problems.