Fixed multi-attribute parsing

[iskandr]

• Last PR with multi-attribute parsing still only returned one of multiple tags, this PR actually works
• Added unit test with data from issue #2
• Fixed Travis deploy secure key

[coveralls]

Pull Request Test Coverage Report for Build 52

• 5 of 6 (83.33%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 91.765%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
gtfparse/attribute_parsing.py	5	6	83.33%
<!--	Total:	5	6	83.33%	-->

Totals
Change from base Build 50:	0.0%
Covered Lines:	156
Relevant Lines:	170

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💛 - Coveralls