Compile warning on OSX

[smikes]

CXX(target) Release/obj.target/CppUnitLite/node_modules/cppunitlite/src/Failure.o ../node_modules/cppunitlite/src/Failure.cpp:30:16: warning: conversion from string literal to 'char *' is deprecated [-Wdeprecated-writable-strings] char *part1 = "expected "; ^ ../node_modules/cppunitlite/src/Failure.cpp:31:16: warning: conversion from string literal to 'char *' is deprecated [-Wdeprecated-writable-strings] char *part3 = " but was: "; ^ 2 warnings generated.