fix document bug (#71)

README.md

@@ -62,7 +62,7 @@ manually, you can install newer version of Go into your `GOPATH`:
 1. Clone this repository:
 
     ```
-    $ git clone github.com/librespeed/speedtest-go
+    $ git clone https://github.com/librespeed/speedtest-go
     ```
 
 2. Build
@@ -165,4 +165,4 @@ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU Lesser General Public License
-along with this program.  If not, see <https://www.gnu.org/licenses/lgpl>.
+along with this program.  If not, see <https://www.gnu.org/licenses/lgpl>.