Address all cases of obsolete parsing

[whatyouhide]

This PR supersedes https://github.com/elixir-gettext/expo/pull/94. I took a different approach: collapsing #~ as a post-tokenization step, in order to simplify the grammar.

Fixes #91

[coveralls]

Pull Request Test Coverage Report for Build 1865e71a1f5a58b632982d30c1d16cfc2738cdf3-PR-99

• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 6cf039f7272df5d23f69b89b4da4f54128e9fd1d:	0.0%
Covered Lines:	329
Relevant Lines:	329

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💛 - Coveralls