Prepared to release 0.2.15
Switched off warnings in default C build script
Fixed bug in C compilation when specifying :all cells in a sheet are settable
Updating examples
Tiny cleanup of simplify_arithmetic
Fixed formula parser to cope with comparisons with string joins
SUMIF and SUMIFS can now cope with being passed ranges for the criteria
Cleaned up the examples a tiny bit
The ruby version of IF() now treats 0 as false and all other numbers as true
Remove example pathway output from version control
Added a workaround for brackets not being removed in some cases
 Fix for SUMIF different sized ranges when fixed references are used
Parser now picks up external named references
References to blank cells now return 0 not blank
Ruby version of LEN now distinguishes zeros that are blank from zeros that are not
Typo fix
Changed order of array replacement