Update install.sh

Added more efficient option to detect number of cores on running system via nproc

install.sh

@@ -47,6 +47,9 @@ function python_finder {
 }
 
 function num_cores {
+  if [[ -e /bin/nproc ]]; then
+   num_cpus=$(nproc)
+  else
     num_cpus=1
     if [[ `uname -s` == "Linux" ]]; then
       num_cpus=$(grep -c ^processor /proc/cpuinfo)
@@ -54,9 +57,11 @@ function num_cores {
       # Works on Mac and FreeBSD
       num_cpus=$(sysctl -n hw.ncpu)
     fi
+  fi
   echo $num_cpus
 }
 
+
 function install {
   ycm_dir=`pwd`
   build_dir=`mktemp -d -t ycm_build.XXXXXX`