Broken links documentation

[olivierbonte]

Hi,

First of all, a major thanks to @bgctw for this package, I really enjoyed using it so far!

Since the package has been moved from the personal github of @bgctw to the EarthyScience organisation, the url of where the documentation is hosted has changed, but this has not yet been updated in the README.

[olivierbonte]

To fix this, I have changed the urls in #43 to close this issue. Note that for codecov, I kept the original https://app.codecov.io/gh/bgctw/Bigleaf.jl as this still seems to work.

[bgctw]

Thank you @olivierbonte for reminding me to update the links and for you pull request. Rather than merging you PR, I consistently replaced all references to bgctw also across other files, and changed also the codecov setup.