Add area weighted average function.

See merge request !7

update zxc with master (delete tmp2.md)

small change to run.r

See merge request !6

Form adjustment for mon_mean.r and run.r

See merge request !5

delete tmp2.md

See merge request !4

small change to read_netcdf.r

See merge request !3

merge by command

fix

test

See merge request !2

test

Add 3 files about monthly mean

See merge request !1