Update README punctuation lines 34, 55, 60 and 62

line 34 was previously awkward to read. It would read better either as "Fetch all node dependencies" or "Fetch all of the node dependencies" :
### Fetch all the node dependencies
--> should now read -->
### Fetch all node dependencies

Fixed plurality on line 55:
This tasks uses unminified... (rest of line unchanged)
--> should now read -->
This task uses unminified... (rest of line unchanged)

Added missing period line 60:
Add unit tests Unit tests can be found... (rest of line unchanged)
--> should now read -->
Add unit tests. Unit tests can be found... (rest of line unchanged)

Added two missing periods line 62:
Add an issue and send a pull request Pull requests are easier to track if you also include an issue. Sending a pull request from a branch makes it easier for you to resolve conflicts in master
--> should now read -->
Add an issue and send a pull request. Pull requests are easier to track if you also include an issue. Sending a pull request from a branch makes it easier for you to resolve conflicts in master.