Ensure `location` is honoured

[andrie]

• Bug fix that didn't honour folder location
• Use only base R - remove dependency on stringr
• Use read.dcf() to read DESCRIPTION

[andrie]

• Fix more instances of functions that do not have location argument;
• Simplify github access functions using git2r;
• Fix documentation issue;
• Rebuild docs

[RMHogervorst]

This is amazing work! Thanks Andrie!