Edit README.md
Edit README.md

Edit file, mostly for active voice and removal of marketing language.
kjbracey-arm/mbed,andcor02/mbed-os,andcor02/mbed-os,kjbracey-arm/mbed,mbedmicro/mbed,mbedmicro/mbed,kjbracey-arm/mbed,kjbracey-arm/mbed,mbedmicro/mbed,andcor02/mbed-os,andcor02/mbed-os,andcor02/mbed-os,mbedmicro/mbed,andcor02/mbed-os,mbedmicro/mbed