Nth PR on develop branch for easybuild-docs, for N=5

still bits and pieces to improve, but ok to receive the first round of feedback
Don't underestimate how much people struggle with GCC, cfr. http://stackoverflow.com/questions/13500987/is-it-possible-to-install-g-on-centos-without-root/13501191#13501191 (check the top answer there ;-)).

I agree the GCC example is one that requires patience when tried, but jumping in with toolchain, `--robot` and everything is too much at the very beginning since it all needs to be explained.

Also, it's typically what `eb` will do first (maybe hidden as part of a robot build, but fine). So it's very relevant as a first example imho.

Maybe a note and/or an additional paragraph should be added that typical usage of `eb` involves using a toolchain that was installed before:

```
$ eb goolf-1.4.10.eb  # includes GCC-<version>
...
$ eb bzip2-1.0.6-goolf-1.4.10.eb
```