Network: Follow redirects (up to 15 times)

[thomastanck]

Resolves #174.

Summary of changes:

• Refactor network to fully use async-http-client
• Follow redirects

[coveralls]

Pull Request Test Coverage Report for Build 988

• 30 of 35 (85.71%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.1%) to 91.127%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/main/java/seedu/address/util/Network.java	30	35	85.71%
<!--	Total:	30	35	85.71%	-->

Totals
Change from base Build 987:	-0.1%
Covered Lines:	2547
Relevant Lines:	2795

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💛 - Coveralls

[qjqqyy]

Should be good iff tests pass