Contrast improvements for the dark theme

Included are several suggestions for improving the contrast in the dark theme. The table is coloured just like the screenshots actually.

Here is a summary of the changes:

Javascript arguments before:

![js2-mode-old](https://f.cloud.github.com/assets/159257/1800916/a54b181a-6bd7-11e3-917b-3f5e113fb798.png)

Javascript arguments after:

![js2-mode-new](https://f.cloud.github.com/assets/159257/1800915/a54a8300-6bd7-11e3-96ad-bd0666463ec9.png)

Org mode links, dates, and tables before:

![org-mode-old](https://f.cloud.github.com/assets/159257/1800917/a54c3a56-6bd7-11e3-8762-96c37ff18bf4.png)

Org mode links, dates, and tables after:

![org-mode-new](https://f.cloud.github.com/assets/159257/1800918/a54c6a9e-6bd7-11e3-98b7-601bbadef670.png)