Save unknown update

[stewartjarod]

Summary:

Fixing issue with Model Updates with unknown attributes

GitHub linked issue:

#403

Other information:

Type (select 1):

• Bug fix
• Feature implementation
• Documentation improvement
• Testing improvement

• Test added to report bug (GitHub issue #--- @---)
• Something not listed here

Is this a breaking change? (select 1):

• 🚨 YES 🚨
• No
• I'm not sure

Is this ready to be merged into Dynamoose? (select 1):

• Yes
• No

Are all the tests currently passing on this PR? (select 1):

• Yes
• No

Other:

• I have searched through the GitHub pull requests to ensure this PR has not already been submitted
• I have updated the Dynamoose documentation (if required) given the changes I made
• I have added/updated the Dynamoose test cases (if required) given the changes I made
• I have run npm test from the root of the project directory to ensure all tests continue to pass
• I agree that all changes made in this pull request may be distributed and are made available in accordance with the Dynamoose license
• All of my commits and commit messages are detailed, explain what changes were made, and are easy to follow and understand
• I have confirmed that all my code changes are indented properly using 2 spaces
• I have filled out all fields above

[stewartjarod]

@fishcharlie Think we can get this in soon?

[coveralls]

Pull Request Test Coverage Report for Build 658

• 13 of 18 (72.22%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.02%) to 84.577%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/Model.js	13	18	72.22%

Totals
Change from base Build 654:	-0.02%
Covered Lines:	1855
Relevant Lines:	2119

---

💛 - Coveralls

[fishcharlie]

@stewartjarod Let's do it!! 😃