Merge pull request #4 from mikel-egana-aranguren/master

Mas contenido
Introduction modified with biodiversity references
Merge branch 'master' of https://github.com/alejandroriglesias/PPIO_SWJ

Conflicts:
	PPIO_SWJ.pdf

Changes introduced
pdf modified with mikel new content and introduction also modified
NCBI_552 initial diagram added
LaTex template modified: introduction modified with minor changes, and modelling modified with more content
Ontology diagram modified
Discussion section modified and minor changes in other sections
LaTex template modified, new bibliographic entry in the .bib file (Wieczorek), and NCBITaxon_552 diagram modified)
Merged