Bump solidity-parser to 0.3.0

[cgewecke]

• Upgrades solidity-parser (pins to 0.3.0)
• Removes array check from body node parsing to match new AST format in solidity-parser
• Adds stub for StateVariableDeclaration node in parse.js. (These are top level declarations that don't get coverage.)
• Adds coverage test for a tuple declaration
• Resolves #25 (possibly #16 as well).

[codecov-io]

Codecov Report

Merging #56 into master will increase coverage by 0.33%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #56      +/-   ##
==========================================
+ Coverage   98.28%   98.62%   +0.33%     
==========================================
  Files           6        6              
  Lines         291      290       -1     
  Branches       39       38       -1     
==========================================
  Hits          286      286              
+ Misses          5        4       -1

Impacted Files	Coverage Δ
parse.js	97.4% <100%> (+1.24%)	:arrow_up:

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