Initial experimentation with Travis CI configuration

This is not intended to replace Jenkins immediately, and Jenkins will remain the CI of reference for merging pull requests in the near term.  Long term, it is possible that Travis will give us better integration with github, so we are investigating its use.

Author: Michael Armbrust <michael@databricks.com>

Closes #230 from marmbrus/travis and squashes the following commits:

93f9a32 [Michael Armbrust] Add Apache license to .travis.yml
d7c0e78 [Michael Armbrust] Initial experimentation with Travis CI configuration

.travis.yml

+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+ 
+ language: scala
+ scala:
+   - "2.10.3"
+ jdk:
+   - oraclejdk7
+ env:
+  matrix:
+   - TEST=sql/test
+   - TEST=hive/test
+   - TEST=catalyst/test
+   - TEST=streaming/test
+   - TEST=graphx/test
+   - TEST=mllib/test
+   - TEST=graphx/test
+   - TEST=bagel/test
+ cache:
+   directories:
+     - $HOME/.m2
+     - $HOME/.ivy2
+     - $HOME/.sbt
+ script:
+   - "sbt ++$TRAVIS_SCALA_VERSION scalastyle $TEST"