Add newline after dedent in lexer

[JSAbrahams]

Relevant issues

Resolves #219

Summary

Lexer now always adds a newline after a dedent so a block is always followed by a dedent.

Update if else parsing logic to deal with newline after dedent. Weirdly it seems like this was the only location where the parser had to be updated after this pretty big change.

Added Tests

• Unit tests for lexer
• Unit tests for parsing if expression and statement
• Unit tests for parsing a few variations of a class

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (develop@da1685c). Click here to learn what that means. The diff coverage is n/a.

@@            Coverage Diff             @@
##             develop     #236   +/-   ##
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  Coverage           ?   79.90%           
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  Files              ?       99           
  Lines              ?     8732           
  Branches           ?        0           
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  Hits               ?     6977           
  Misses             ?     1755           
  Partials           ?        0           

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