Improve user experience at installing mbed tools

[MarceloSalazar]

Currently, we need to install Python, pip, git, mercurial, mbed-cli.

maybe @screamerbg and @BlackstoneEngineering can help?

[BlackstoneEngineering]

mbed-CLI should not be distributed via pip this time, we should bundle it up into our own .exe installer and .app for mac. pip burned us last time and I reguard it as an unstable method for distributing software (especially in China).

See the following for examples.
https://github.com/ARMmbed/yotta_osx_installer
https://github.com/ARMmbed/yotta_windows_installer

For reference I believe the windows installer method is solid, but i would suggest finding a new method for OSX as I have not been able to replicate a distributable virtual environment since.

@theotherjimmy should be able to provide some better insights here where I messed up.

[screamerbg]

There is already Windows installer. and @BlackstoneEngineering is working on Mac installer. @MarceloSalazar are you happy to write a new feature requirement for installers that bundle up Mbed CLI, python modules, git, hg, and latest Mbed OS for pre-cached operation. cc @arekzaluski about having Mbed OS git index as part of the installer which can be used as pre-populated cache.

[BlackstoneEngineering]

Im glad to see we're actually making progress on this. for reference, https://github.com/blackstoneengineering/mbed-cli-osx-installer is where i'm working on the OSX installer. It will be moved to /ArmMbed once it is ready for use / distribution. Hopefully soon.

After that I am planning on making a get_mbed_cli.py that will function similar to get_pip.py so at least we have instructions that say 'run a script' instead of the 10+ pages we currently have.