Method Changes

**MD5Model.h
- Changed method from a - (NSString *) getMD5String to + (NSString *)
getMD5String:(NSString *)input;
- Removed properties inputText & outputText
- Adjusted comments to reflect what is being done
**MD5Model.m
- Change method from a - (NSString *) getMD5String to + (NSString *)
getMD5String:(NSString *)input
- Removed calls to properties
- Adjusted comments to reflect what is being done