Closes #1890 and #1900 to properly check for dates and fix other bugs in checkSpec

[lauramaxwell]

Overview

• allows users to specify Dates in spec and checkspec will properly check the type
• changes from checking mode() to checking class() in checkSpec
  • most numeric types were converted to integer to pass this check.
• add testing for Date functionality

Test Notes/Sample Code

Connected Issues

• Closes #1890
• Closes #1900