Merge pull request #10 from richardadalton/master

String Calculator in F# Without Regex
Merge pull request #11 from richardadalton/master

Type-Driven rather than Test-Driven Approach
Merge pull request #12 from richardadalton/master

Fix parsing of Default and Custom Delimiters in same expression
Merge pull request #13 from richardadalton/master

Modified Add function to "Point Free" style