Reworked installation instructions.
Reworked installation instructions.

In particular, on Linux we now use pre-built binaries.

Fixes #92.

GoogleCloudPlatform/gcsfuse,BanzaiMan/gcsfuse,GoogleCloudPlatform/gcsfuse,mbrukman/gcsfuse,BanzaiMan/gcsfuse,kahing/gcsfuse,GoogleCloudPlatform/gcsfuse