Add section on using source control

new file: 	source_files/.gitignore
modified: 	source_files/cc_presentation_sourcecontrol
modified: 	source_files/codecumbria_sourcecontrol.20130227.lyx
Added images

new file: 	source_files/adding-files.svg
new file: 	source_files/branching.svg
new file: 	source_files/centralised.svg
modified: 	source_files/codecumbria_sourcecontrol.20130227.lyx
new file: 	source_files/distributed.svg
new file: 	source_files/merging.svg
new file: 	source_files/tagging.svg
new file: 	source_files/images/adding-files.dia
new file: 	source_files/images/branching.dia
new file: 	source_files/images/centralised.dia
new file: 	source_files/images/distributed.dia
new file: 	source_files/images/merging.dia
new file: 	source_files/images/tagging.dia
Added talk slides

new file:   sourcecontrol.20130227.odp
Added github url

modified:   sourcecontrol.20130227.odp
Merge branch 'release/1.0'

Conflicts:
	source_files/.gitignore