Merge pull request #1 from majeau-bettez/master

minor: improve readme
fix typo
Merge github.com:NTNU-IndEcol/industrial_ecology
minor: ignore CH4 for CAS matching

In addition to ignoring CO2, also ignore CH4
Because some is from fossile and some from biogenic with very different
characterisations.
	modified:   match_characterisation.m