Selector: Forget about elements after testing them

Fixes gh-299
Closes gh-300
Revert "Tokenization: Remove "#" exception for identifier tokens"

This reverts commit f204a6112216f31685717d9fc1bf6cabf42b2ef1.

Conflicts:
	dist/sizzle.js
	dist/sizzle.min.js
	dist/sizzle.min.map
Revert "Revert "Tokenization: Remove "#" exception for identifier tokens""

This reverts commit 2280ab78b0e19dc494f9c47fd1f4a42dd63c280d.
Selector: Use valid XHTML in support tests

Fixes gh-304
Ref aca006dd2d3fb3c407ff99bb25153852d73e0f6b
Ref jquery/jquery#1969
Tests: Test attribute selectors in smaller units

Closes gh-302