simplify install.html so that it doesn't require GNU make

[zooko]

Our docs/install.html presently says, in sum:

1.  Install g++, GNU make, and Python
2.  Run "make"
3.  Run "make test"
4.  Run "./bin/tahoe"

This ticket is to simplify this to say:

1.  Install g++ and Python
2.  Run "python ./setup.py build_tahoe"
3.  Run "python ./setup.py trial"
4.  Run "./bin/tahoe"

Here is the end of the recent discussion about this on the mailing list: ​http://allmydata.org/pipermail/tahoe-dev/2008-September/000802.html

What that says is that bugs like #455 are preventing this new simpler recipe from working.

[cgalvan]

The install.html has been updated as indicated in the ticket description so this ticket can be closed.