Installing mbed-os dependencies

Author: Mohammad Azim Khan

.travis.yml

@@ -6,6 +6,7 @@ script:
 - mbed config root .
 # Pull in mbed-os and other dependencies
 - mbed deploy
+- sudo pip install -r mbed-os/requirements.txt
 - mbed compile --clean -m K64F -t GCC_ARM
 - mbed compile --clean -m K64F -t GCC_ARM --profile debug
 
@@ -19,4 +20,8 @@ before_install:
 
 install:
 - sudo pip install mbed-cli==0.9.10
+- sudo pip install pytest
+- sudo pip install pylint
+- sudo pip install hypothesis
+- sudo pip install mock