Feature/validate with soap

[jesserobertson]

Fixes #4

Implements validators against the SOAP schema which give reasonably sensible errors (KeyError when a key is wrong, ValueError when a constraint is violated) so we can bake this into other parts of the library.

[coveralls]

Pull Request Test Coverage Report for Build 55

• 60 of 68 (88.24%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-1.0%) to 89.634%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
earthchem/validation.py	60	68	88.24%

Totals
Change from base Build 50:	-1.0%
Covered Lines:	147
Relevant Lines:	164

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 55

• 60 of 68 (88.24%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-1.0%) to 89.634%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
earthchem/validation.py	60	68	88.24%

Totals
Change from base Build 50:	-1.0%
Covered Lines:	147
Relevant Lines:	164

---

💛 - Coveralls

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (develop@0de6e87). Click here to learn what that means.
The diff coverage is 88.23%.

@@            Coverage Diff             @@
##             develop      #10   +/-   ##
==========================================
  Coverage           ?   89.63%           
==========================================
  Files              ?        4           
  Lines              ?      164           
  Branches           ?        0           
==========================================
  Hits               ?      147           
  Misses             ?       17           
  Partials           ?        0

Impacted Files	Coverage Δ
earthchem/validation.py	88.23% <88.23%> (ø)

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