Merge pull request #18 from CrowdProcess/error_handling

add error handling formulas
Add test cases for ISERR, ISERROR and IFERROR
Merge POWER pull request
Merged several pull requests, added grunt support for creating a bundle
Consolidate Formula.IFERROR implementations
Linting
Straightforward IF Formula
V0.0.27
PROPER : return undefined if input is
merge upstream