adding a few more Fibonacci algorithms

+fibonacciWithDecimal: uses NSDecimalNumber and can get up to the 186th
number
Merge pull request #25 from aceisScope/master

LCS and LD for NSString
Update README.md
Code formate.
Merge branch 'master' of https://github.com/EvgenyKarkan/EKAlgorithms
Nth prime added.
Update README.md
Merge pull request #26 from flohei/master

adding a few more Fibonacci algorithms
Minor code formatting.