Use CoffeeScript literal syntax for links to other methods/properties

Foo::bar for instance methods/properties
Foo.bar for class methods/properties
Don't clobber diff module with local variable
Update syntax of links in internal docs
Update syntax of links in specs
Properly generate links to instance methods

Previously, we only chopped off the leading `.` character. Now we need
to chop off the leading `::`.
Use :: and . instead of . and @ in generated method signatures
Update specs for new signature format
Restore trailing newlines that cause markdown to emit a <br>
Merge pull request #27 from atom/ns-coffee-script-link-syntax

Expect CoffeeScript literal syntax in links to class and instance methods