Make library URLs easier to copy+paste

I find myself often visiting cdnjs to copy+paste libraries for various projects, but the actual act of copy+pasting is a bit challenging at present. I'm hoping to remedy this situation :)

This commit includes the following changes:
- wrap library URLs in readonly input boxes
- select readonly contents on hover
- remove outer table border (looked ugly with input boxes)
- make version button stand out against input box
- consistent whitespace (tabs to spaces)