Improve documentation

[MartinKielhornPhilips]

Hi,
I'm currently trying kubler for the first time.
To make the first build run fast, it would be helpful to note how to set BOB_MAKEOPTS.

I propose to add one sentence (fat font) to the README.md:

Initial Configuration

Kubler doesn't require any further configuration but you may want to review the main config file
located at /etc/kubler.conf. Change BOB_MAKEOPTS='-j9' to reflect the number of processors in your system. If the file doesn't exist the kubler.conf file in Kubler's root folder is
used as a fallback.

[edannenberg]

Hey, thanks for reporting! Good idea, I'm a bit short of time currently, I'll add it probably next week.