Adding Travis config and shell scripts to build wheels.

[dhermes]

@silvolu Please take a look.

Notice I added a ## When will a new build occur section to the README since you last reviewed.

[dhermes]

Also, we'll need to update the REAMDE a bit with an integration strategy since both sides kind of depend on each other.

I think it should go as follows:

1. Get the skeleton in place (this commit).
2. Add a custom_pip_install.sh file to gcloud-python that doesn't actually depend on the wheels yet.
3. Make a commit to this repo (i.e. a ``LATEST_COMMIT` file) to kick off a build of the wheelhouse.
4. After the wheelhouse is built, alter custom_pip_install.sh in gcloud-python to try to use the wheelhouse first and then update (as described in the README here)

Also, for reference this is most of the fix for googleapis/google-cloud-python#290

[silvolu]

Can you add license headers to the .sh files, as shown in line 3-15 of e.g. merge.sh from gcloud-python?

[dhermes]

Addressed and git push -fed as part of original commit.

[silvolu]

Should we move setting all the env variables for configuration to the Travis UI and just leave a commented out list of variables that need to be set here? That would arguably make it easier to use the script across repos (setting on web interface vs changing local files)

[dhermes]

Good call.

I put them at the top so people would know what to change if they wanted to do the same thing for other projects.

I also see that I stupidly (d'oh) left my hacks in there to make Travis run on my own fork.

[silvolu]

I forgot to add: your plan in 4 steps SGTM

[dhermes]

OK @silvolu I smashed your changes into a single commit and git push -fed.

I also went through the steps in the README and set up this repository to do the builds.