Fix README links, they need to be absolute and not relative to the project
Remove minor warnings seen with GCC ARM toolchain

[Warning] Gap.h@152: 152:16: warning: enumeration value
‘GAP_EVENT_CONNECTED’ not handled in switch [-Wswitch] enumeration value
‘GAP_EVENT_DISCONNECTED’ not handled in switch [-Wswitch]

[Warning] GattServer.h@78: In member function ‘void
GattServer::handleEvent(GattServerEvents::gattEvent_e, uint16_t)’:
enumeration value ‘GATT_EVENT_DATA_SENT’ not handled in switch
[-Wswitch]

[Warning] GattServer.h@78: In member function ‘void
GattServer::handleEvent(GattServerEvents::gattEvent_e, uint16_t)’:
enumeration value ‘GATT_EVENT_DATA_WRITTEN’ not handled in switch
[-Wswitch]

[Warning] GattServer.h@78: In member function ‘void
GattServer::handleEvent(GattServerEvents::gattEvent_e, uint16_t)’:
enumeration value ‘GATT_EVENT_READ_AUTHORIZATION_REQ’ not handled in
switch [-Wswitch]

[Warning] GattServer.h@78: In member function ‘void
GattServer::handleEvent(GattServerEvents::gattEvent_e, uint16_t)’:
enumeration value ‘GATT_EVENT_WRITE_AUTHORIZATION_REQ’ not handled in
switch [-Wswitch]
Merge pull request #23 from shirishb/master

Fix README links