feat: enable doc deployment on master pushes and install pygments lexer before build

.travis.yml

@@ -9,13 +9,13 @@ env:
   - WREN_OPTIONS="" CI_ARCHS="ci_32 ci_64"
   - WREN_OPTIONS="-DWREN_NAN_TAGGING=0" CI_ARCHS="ci_64"
 
-# TODO: Enable this once the TODOs in util/deploy_docs_from_travis.sh are fixed.
-# jobs:
-#   include:
-#     - stage: deploy
-#       script: bash util/deploy_docs_from_travis.sh
-#       # Only deploy commits that land on master.
-#       if: branch = master and type = push
+# Automatically build and deploy docs.
+jobs:
+  include:
+    - stage: deploy
+      script: bash util/deploy_docs_from_travis.sh
+      # Only deploy commits that land on master.
+      if: branch = master and type = push
 
 # Travis VMs are 64-bit but we compile both for 32 and 64 bit. To enable the
 # 32-bit builds to work, we need gcc-multilib.