Avoid frequent forking of new processes.

This pull request is to avoid frequent forking of new processes, which causes slowness due to the overhead involved, and if it can be avoided entirely would double the effective memory availability. 

Original title: "Recent changes to GATPFit break things, sometimes."
---
On some computers, the recent changes to GATPFit cause `make test` to hang, very near the start, at the line

```
Reading Lennard-Jones database from /home/rwest/Code/RMG-Java/databases/RMG_database/transport_groups/
```

When pressing ctrl-C, in then reports the error

```java
ERROR: jing.chem.GATPFitException: no output from GATPFit
    at jing.chem.GATPFit.callGATPFit(GATPFit.java:203)
    at jing.chem.GATPFit.generateNASAThermoData(GATPFit.java:259)
    at jing.chem.Species.generateNASAThermoData(Species.java:362)
    at jing.chem.Species.<init>(Species.java:120)
    at jing.chem.Species.make(Species.java:874)
    at jing.rxnSys.ReactionModelGenerator.populateInitialStatusListWithReactiveSpecies(ReactionModelGenerator.java:4890)
    at jing.rxnSys.ReactionModelGenerator.initializeReactionSystems(ReactionModelGenerator.java:562)
    at jing.rxnSys.ReactionModelGenerator.modelGeneration(ReactionModelGenerator.java:1312)
    at RMG.main(RMG.java:96)

ERROR: jing.chem.NASAFittingException: Error in running GATPFit: jing.chem.GATPFitException: Error running GATPFit
jing.chem.GATPFitException: no output from GATPFit
To help diagnosis, writing GATPFit input to file GATPFit/INPUT.txt

    at jing.chem.GATPFit.generateNASAThermoData(GATPFit.java:262)
    at jing.chem.Species.generateNASAThermoData(Species.java:362)
    at jing.chem.Species.<init>(Species.java:120)
    at jing.chem.Species.make(Species.java:874)
    at jing.rxnSys.ReactionModelGenerator.populateInitialStatusListWithReactiveSpecies(ReactionModelGenerator.java:4890)
    at jing.rxnSys.ReactionModelGenerator.initializeReactionSystems(ReactionModelGenerator.java:562)
    at jing.rxnSys.ReactionModelGenerator.modelGeneration(ReactionModelGenerator.java:1312)
    at RMG.main(RMG.java:96)

CRITICAL: Error in running GATPFit: jing.chem.GATPFitException: Error running GATPFit
jing.chem.GATPFitException: no output from GATPFit
To help diagnosis, writing GATPFit input to file GATPFit/INPUT.txt


RMG execution terminated at 2012-06-08 12:57:36
make: *** [test] Error 130
```

@nickvandewiele reports the same problem.

This problem occurs for me on a linux cluster with 

```
gfortran -v
Using built-in specs.
COLLECT_GCC=gfortran
COLLECT_LTO_WRAPPER=/share/apps/gcc452/libexec/gcc/x86_64-unknown-linux-gnu/4.5.2/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-4.5.2/configure --prefix=/share/apps/gcc452
Thread model: posix
gcc version 4.5.2 (GCC)

java -version
java version "1.6.0_13"
Java(TM) SE Runtime Environment (build 1.6.0_13-b03)
Java HotSpot(TM) 64-Bit Server VM (build 11.3-b02, mixed mode)
```

It works fine for me on my mac with
```
gfortran -v
Using built-in specs.
Target: i686-apple-darwin11
Configured with: /Volumes/Media/Builds/gcc-5666.3/build/obj/src/configure --disable-checking --prefix=/usr --mandir=/share/man --enable-languages=c,objc,c++,obj-c++,fortran --program-transform-name=/^[cg][^.-]*$/s/$/-4.2/ --with-slibdir=/usr/lib --build=i686-apple-darwin11 --program-prefix=i686-apple-darwin11- --host=x86_64-apple-darwin11 --target=i686-apple-darwin11 --with-gxx-include-dir=/include/c++/4.2.1
Thread model: posix
gcc version 4.2.1 (Apple Inc. build 5666) (dot 3)

java -version
java version "1.6.0_31"
Java(TM) SE Runtime Environment (build 1.6.0_31-b04-415-11M3635)
Java HotSpot(TM) 64-Bit Server VM (build 20.6-b01-415, mixed mode)

```