Save button & some gui tweaks

This addresses #70. After some research, it looks like it's not possible to open up emails with attachments already there. I didn't spend much time looking for a workaround, as we'll eventually move to uploading directly to the wca website.

I also added the TEST_FILE and TEST_JSON_EXPORT variables to WorkbookAssistantFrame for development purposes.

I also copied some code I found onstackoverflow to address this particularly annoying sizing issue with the JSON export window on Windows.

Before:

![screenshot 2014-03-01 10 31 58](https://f.cloud.github.com/assets/277474/2302362/977d5b04-a178-11e3-9195-febcb7ea8217.png)

After:

![screenshot 2014-03-01 10 33 22](https://f.cloud.github.com/assets/277474/2302363/978e261e-a178-11e3-8441-1032db791f9f.png)