Navigate on paste

Middle click on a page navigates to the content of the primary selection. Requires Linux.On Linux, middle click triggers a paste action. With this extension, middle clicking on part of a tab that wouldn't normally accept a paste action will cause the tab to navigate to the contents of the PRIMARY selection. Due to restrictions of the extension system, it does not work on the new tab page, or any other chrome:// page. However, there is an option to load a blank page instead of the new tab page.

Changes:
v 0.7.1
- Update manifest to version 2; this may help with the regression bug where a new tab was opened as well.
- Removed unneeded permission "tabs"
- Added option to load a specific URL to the new tab page.

v 0.6
- Bug fix: new tab behavior didn't work correctly until it was clicked.
- Bug fix: cut and paste handling for URL matching regex were broken.

v 0.5 Thanks to Adam Katz and Simon Schubert for the improvements.
- Strip leading and trailing whitespace from clipboard contents.
- Add option to navigate only if clipboard contents match a regular expression.
- Make labels on options page clickable.

v 0.4
- Add option to open new tabs instead of replacing the current tab.
- Add option to replace the new tab page with a blank page that supports middle click to navigate.

v 0.3
- Bug fix: some types of input areas were not properly detected, triggering navigation if the user tried to paste into them. (Content-editable divs, as used for the status update on Facebook.)