chore: adds a link to the nmt specs (#174)

## Overview
A mini PR to close #98 

## Checklist

- [x] New and updated code has appropriate documentation
- [x] New and updated code has new and/or updated testing
- [x] Required CI checks are passing
- [x] Visual proof for any user facing features like CLI or
documentation updates
- [x] Linked issues closed with keywords

README.md

@@ -102,7 +102,6 @@ This implementation was heavily inspired by the initial implementation in the ce
 [@musalbas]: https://github.com/musalbas
 
 [prototype]: https://github.com/celestiaorg/lazyledger-prototype
-[NebulousLabs']: https://gitlab.com/NebulousLabs/merkletree
 
 ## Contributing
 

nmt.go

@@ -1,4 +1,5 @@
 // Package nmt contains an NMT implementation.
+// The specifications can be found in https://github.com/celestiaorg/nmt/blob/master/docs/spec/nmt.md.
 package nmt
 
 import (