Darken borders of input boxes and courseware div separation

Before:
![image](https://cloud.githubusercontent.com/assets/596029/4909228/ae68a44c-6471-11e4-9181-749e5e8785e9.png)

After:
![image](https://cloud.githubusercontent.com/assets/596029/4909242/c1c71622-6471-11e4-93cf-c5eae3040b68.png)

It has been really hard to see text input boxes and such on an older monitor I have. Any objections to darkening these borders 18.5% ? @ichuang @JoeMartis @Ferdi @pdpinch