Support for binary AND and OR operators

[slintak]

I have added support for two binary operators -- & and |.

There are more unsupported operators I did not add. For example bitwise shifts << and >>. I was not able to implement these as they consists of two characters. I would need some help to implement them.

[coveralls]

Pull Request Test Coverage Report for Build 34

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 39 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.003%) to 97.501%

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Files with Coverage Reduction	New Missed Lines	%
./minify.lua	39	98.52%

Totals
Change from base Build 33:	0.003%
Covered Lines:	1795
Relevant Lines:	1841

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💛 - Coveralls