Add installation instructions in case you don't have superuser access

[dima74]

There is the following text at the top of https://mosh.org:

You don't need to be the superuser to install or run Mosh

However it is unclear how to install mosh on server if you don't have root rights.

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Could you, please, add instructions about installing mosh without root access. I think for now it can be just for one popular distribution, for exampe ubuntu.

Something like this gist: https://gist.github.com/xiaom/8264691 (code from gist doesn't work now, but there are some useful notes in comments, I think it would be very cool if you will accumulate these notes and publish remade gist on your site).

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Thanks for excellent tool!