Check for infinite / nan initialization 

#### Summary:

Stops the initialization if initialization is infinite or nan on the unconstrained scale.

#### Intended Effect:

Checks to see if the initialization on the unconstrained scale is +inf, -inf, or nan, stops initialization if the invalid, and provides a message with the unconstrained first invalid variable name and the value that it took.

#### How to Verify:

Added unit test.
Could also verify by providing an R dump initialization file at -inf or +inf.

#### Side Effects:

New message when initialization fails:
`<param name> initialized to invalid value (<param value>)`

#### Documentation:

None. This is the expected behavior. We haven't included error messages in the manual.

#### Reviewer Suggestions: 

Anyone.