Can't find templates when installed using Cargo

Hi!

I followed the steps from the download page:

git clone https://gitlab.com/larswirzenius/subplot
# This checked out commit 14e76f6341af2a02450183cb7514f5ea97d18ebc
cd subplot
cargo build
cargo install --path=.

Then I tried running it on larswirzenius/obnam:

$ git clone https://gitlab.com/larswirzenius/obnam
$ cd obnam
$ sp-codegen obnam.md -o test.py
Error: No such file or directory (os error 2)

If I run the program under strace, I see that it looks for a template in /usr/share/subplot:

$ strace sp-codegen obnam.md -o test.py
---->8-------->8-------->8----
openat(AT_FDCWD, "/usr/share/subplot/python/template.yaml", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
write(2, "Error: ", 7Error: )                  = 7
write(2, "No such file or directory", 25No such file or directory) = 25
write(2, " (os error ", 11 (os error )             = 11
write(2, "2", 12)                        = 1
write(2, ")", 1))                        = 1
write(2, "\n", 1
)                       = 1
sigaltstack({ss_sp=NULL, ss_flags=SS_DISABLE, ss_size=8192}, NULL) = 0
munmap(0x7f51e7a79000, 12288)           = 0
exit_group(1)                           = ?
+++ exited with 1 +++

There is indeed no such file, and no /usr/share/subplot even.

Installing from the APT repo at ci-prod-controller.vm.liw.fi works fine, but I think something still has to be done about the Cargo install (even if it's just removing it from the docs).