Fixed broken .gitignore file and added additional conditions to it

The previous file was named `.gitignore.txt` by mistake (darn windows defaults). This should fix that.
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Just like [the first pull request](https://github.com/owatonnarobotics/2015RobotCode/pull/1), this should ignore unnecessary shortcut files in addition to other binary files like `.jar` archives when committing changes.

I'm positive that we don't need any shortcut files, but I'm not as positive about ignoring the compiled Java. My argument for ignoring them is that git is meant for source code and not binary files that can be compiled elsewhere.