use regex triplet, add unit test

nvm.sh

@@ -98,7 +98,7 @@ nvm_format_version() {
 }
 
 nvm_strip_path() {
-  echo "$1" | sed -e "s#$NVM_DIR/[^/]*$2[^:]*##g" | sed -e "s/::/:/g" | sed -e "s/:$//g"
+  echo "$1" | sed -e "s#$NVM_DIR/[^/]*$2[^:]*:##g" -e "s#:$NVM_DIR/[^/]*$2[^:]*##g" -e "s#$NVM_DIR/[^/]*$2[^:]*##g"
 }
 
 nvm_binary_available() {

test/fast/Unit tests/nvm_strip_path

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+die () { echo $@ ; exit 1; }
+
+. ../../../nvm.sh
+
+TEST_PATH=$NVM_DIR/v0.10.5/bin:/usr/bin:$NVM_DIR/v0.11.5/bin:$NVM_DIR/v0.9.5/bin:/usr/local/bin:$NVM_DIR/v0.2.5/bin
+
+STRIPPED_PATH=`nvm_strip_path "$TEST_PATH" "/bin"`
+
+[ "$STRIPPED_PATH" = "/usr/bin:/usr/local/bin" ] || die "Not correctly stripped: $STRIPPED_PATH "