Use godep for dependencies with vendored source

- [x] Code review (@mattdbridges)
- [x] Developer can build using the wiki (with this branch) (@mattdbridges)

This pull request adds the "godep" binary to the go build.  Currently, pdfcombiner does not build as the cloudwatch library has changed.  This adds the godep tool to vendor our library source into the ```Godeps/_workspace``` directory.

### JIRA

https://peopleadmin.atlassian.net/browse/PA-13173

### Wiki

There is a "getting started" page for building the PDFCombiner binary.  That's a good place to start.

https://github.com/PeopleAdmin/portals/wiki/PDFCombiner-:-Getting-Started

### Installation

Install godep:

```
  go get github.com/tools/godep
```

The initial dependency list was generated using the following command:

```
  godep save
```

However, this dependency list used the latest version of cloudwatch.  I edited the version SHA in the Godeps.json file to a known good version:

 [ bfa553e3b7d6416a36cb81ff5f379acfb9b93f0d](https://github.com/crowdmob/goamz/commit/bfa553e3b7d6416a36cb81ff5f379acfb9b93f0d)

Using these verisons of the library, the ones specified in the Godeps.json file, I was able to build pdfcombiner using:

```
  godep go build
```