add activity read requests

Add access to these endpoints:
* retrieve an activity
* list athlete activities
* list friends' activities
* list activity zones
* list activity laps

This commit also includes some minor code formatting
add gear read requests

Add access to these endpoints:
* Retrieve gear
add segment read requests

Add access to these endpoints:
* Retrieve a segment
* List starred segments
* Segment leaderboards
* Segment explorer
add stream read requests

Add access to these endpoints:
* Retrieve activity streams
* Retrieve effort streams
* Retrieve segment streams
add club read requests

Add access to these endpoints:
* Retrieve a club
* List athlete clubs
* List club members
* List club activities

This commit also includes some minor code formatting
add segment effort read requests

Add access to these endpoints:
* Retrieve a segment effort
update readme
Merge pull request #2 from JamesChevalier/master

Add all the other GET request endpoints