add specific release install details

Author: danh91

README.md

@@ -44,6 +44,8 @@ Python 3.6.5
 
 OpenShip can be installed with [pip](https://pip.pypa.io/):
 
+For latest dev versions
+
 ```shell
   pip install --process-dependency-links -e git://github.com/OpenShip/openship.git#egg=openship
 ```
@@ -56,6 +58,12 @@ cd openship
 python setup.py install
 ```
 
+For released version (change '@version' at your convenience)
+
+```shell
+pip install --process-dependency-links git+git://github.com/OpenShip/openship.git@v1.0-beta
+```
+
 ## Running the tests
 
 ```shell