Travis-ci integration

Hi!

This change runs the tests of the following 20 subprojects of Finagle in Travis-ci environment:

```
finagle-commons-stats
finagle-core
finagle-exception
finagle-exp
finagle-kestrel
finagle-mdns
finagle-mux
finagle-mysql
finagle-native
finagle-ostrich4
finagle-redis
finagle-serversets
finagle-spdy
finagle-stats
finagle-stream
finagle-stress
finagle-testers
finagle-thrift
finagle-thriftmux
finagle-zipkin
```

And it excludes following 2 subprojects because they don't pass in Travis-ci:

```
fiangle-memcached (MigrationClientTest fails, ClientSpec causes error)
finagle-http (EndToEndTest fails)
```

And to clarify the skipping of these two, I added `echo skip sbt ..` lines in the script section.

And also excludes following 4 subprojects because they don't need to test.

```
finagle-doc
finagle-example
finagle-test
finagle-benchmark
```

Thanks.