Added test to TagProcessorTest, if input line is null, output result is null
Added test to TagProcessorTest, if input line starting with < contains <3 characters, no tag is returned
Added test to TagProcessorTest, added equals & hashCode functions to Tag,return valid type tag when a line contains it.
Added scenarios to the top of each test case, amended assert messages.
Merge pull request #73 from neomatrix369/improveTestCoverage

Improve test coverage. Thanks Mani :)