Accept nonstandard links

Issue
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Currently skrollr-menu will not animate / deal with any hashlinks to the current page unless they are expressed with `href='#xxx'`. This means that absolute links to the current page with hash-links will fail when clicked from that page. 

Example
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The menu of a site has a link with `href='/#mysection'`. This will fail because the preceding `/` causes skrollr-menu not to parse it, even though it should be considered a valid link. 

Changes
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This commit addresses this by including a function to check if a link points to the current page, and also supports any GET parameters that a clicked hash-link may have. 
This is the only part that bothers me, since it's hard to understand what it does. Can these two lines be replaced by `href = link.hash` ?