[Fix] nvm use: fix --silent when version is omitted

Fixed a bug where --silent mode was failing for nvm use I ran a test
 that just ran ```nvm use node --silent``` that I wrote by myself.
 Unfortunately I noticed a bug where it still prints out some messages in
 different cases. This pull request is to fix that bug. * Added in an argument
 called ***quiet***  to the nvm_rc_version() function at *line 339* * Printed
 anything inside the nvm_rc_version() only in the scenario where quiet mode is
 off * Ran the nvm_rc_version() function in quiet mode only if silent mode is
 on in the "use" command of nvm at *line 2990* * Ran *nvm_echo* and *nvm_err*
 inside the "use" command of nvm only in the scenario where silent mode is off
 (There were 4 scenarios where this was forgotten) * Edited the ```nvm
 deactivate``` command to include a silent mode * Changed the help page to
 include the --silent option for ```nvm deactivate``` * Added in aliases for
 the --silent flag in ```nvm deactivate``` and ```nvm use``` * Used silent
 mode inside the ```nvm use``` when running ```nvm deactivate``` inside it and
 silent mode is on A test was attached in the 'test/slow/nvm use' directory.
 It is named *Running "nvm use node --silent" doesn't print anything*. It runs
 ```nvm use node --silent and checks``` and succeeds if the OUTPUT matches the
 EXPECTED_OUTPUT which is *null*  or *''*. When the test was run locally, it
 still ouputed results if someone deleted some contents of the *.nvm/* folder.
 This output was given from the ```nvm deactivate command```. This was the
 reason that the ```nvm deactivate``` was edited to include silent mode.

test/slow/nvm use/Running "nvm use node --silent" doesn't print anything

@@ -0,0 +1,13 @@
+#!/bin/sh
+
+die () { echo "$@" ; exit 1; }
+
+\. ../../../nvm.sh
+
+nvm deactivate 2>&1 >/dev/null || die 'deactivate failed'
+
+OUTPUT=$(nvm use node --silent || die 'nvm use node failed')
+EXPECTED_OUTPUT=""
+
+[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] \
+  || die "'nvm use node --silent' output was not silenced to '$EXPECTED_OUTPUT'; got '$OUTPUT'"