install.sh: Enhance comments of the script.

I removed the comment about using $PATH since it leads to long
installation scripts (which violates the KISS principle). Cf. the
discussion on https://github.com/ipfs/go-ipfs/pull/2504

License: MIT
Signed-off-by: Stephan Kulla <git.mail@kulla.me>

cmd/ipfs/dist/install.sh

 #!/bin/sh
+#
+# Installation script for ipfs. It tries to move $bin in one of the
+# directories stored in $binpaths.
 
 bin=ipfs
 binpaths="/usr/local/bin /usr/bin"
@@ -7,10 +10,6 @@ binpaths="/usr/local/bin /usr/bin"
 # because of missing write permissions.
 is_write_perm_missing=""
 
-# this script is currently brain dead.
-# it merely tries two locations.
-# in the future maybe use value of $PATH.
-
 for binpath in $binpaths; do
   if mv -t "$binpath" "$bin" 2> /dev/null; then
     echo "Moved $bin to $binpath"