README: Clarify that PBS = Portable Batch System (#226)

README.md

@@ -11,7 +11,7 @@ Implemented in this package (the `ClusterManagers.jl` package):
 | Load Sharing Facility (LSF) | `addprocs_lsf(np::Integer; bsub_flags=``, ssh_cmd=``)` or `addprocs(LSFManager(np, bsub_flags, ssh_cmd, retry_delays, throttle))` |
 | Sun Grid Engine (SGE) via `qsub` | `addprocs_sge(np::Integer; qsub_flags=``)` or `addprocs(SGEManager(np, qsub_flags))` |
 | Sun Grid Engine (SGE) via `qrsh` | `addprocs_qrsh(np::Integer; qsub_flags=``)` or `addprocs(QRSHManager(np, qsub_flags))` |
-| PBS              | `addprocs_pbs(np::Integer; qsub_flags=``)` or `addprocs(PBSManager(np, qsub_flags))` |
+| PBS (Portable Batch System) | `addprocs_pbs(np::Integer; qsub_flags=``)` or `addprocs(PBSManager(np, qsub_flags))` |
 | Scyld | `addprocs_scyld(np::Integer)` or `addprocs(ScyldManager(np))` |
 | HTCondor | `addprocs_htc(np::Integer)` or `addprocs(HTCManager(np))` |
 | Slurm | `addprocs_slurm(np::Integer; kwargs...)` or `addprocs(SlurmManager(np); kwargs...)` |