add trivial mypy check

Author: jreback

Diff for: .travis.yml

@@ -74,6 +74,7 @@ matrix:
         - FULL_DEPS=true
         - CLIPBOARD=xsel
         - COVERAGE=true
+        - TYPING=true
         - CACHE_NAME="35_nslow"
 #        - USE_CACHE=true # Don't use cache for 35_nslow
       addons:

Diff for: ci/install_travis.sh

@@ -113,6 +113,10 @@ if [ "$LINT" ]; then
    pip install cpplint
 fi
 
+if [ "$TYPING" ]; then
+   pip install mypy-lang
+fi
+
 if [ "$COVERAGE" ]; then
     pip install coverage pytest-cov
 fi

Diff for: ci/typing.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+
+echo "inside $0"
+
+source activate pandas
+
+RET=0
+
+if [ "$TYPING" ]; then
+
+    echo "Typing  *.py"
+    mypy pandas/core/base.py
+    if [ $? -ne "0" ]; then
+        RET=1
+    fi
+    echo "Typing *.py DONE"
+
+else
+    echo "NOT checking typing"
+fi
+
+exit $RET