Added Fedora build requirements instruction

Added a section where all Fedora necessary requirements are installed
I tested it on Fedora 20 64 bit
syntax corrected
syntax corrected
fix typos
mention reference count bugs
mention section on ref counting and cpychecker
links to the Numpy C-API
tweaks
fix typo
typo discovered during the lecture
Replaced easyinstall with pip

PIP should be used in favor of easy install. Therefore I replaced the package installations with pip.
Merge pull request #112 from guerda/patch-1

Added Fedora build requirements instruction
Merge pull request #114 from esc/improve_interface_with_c

Improve interface with c