version.sh: create requirements.txt with current versions

[matthiasdiener]

Here is how the output looks like:

$ ./version.sh
[...]
*** Creating requirements file with current emirge module versions
git+https://github.com/inducer/pymbolic.git@v2020.1-44-g3ff0732#egg=pymbolic
Warning: missing module 'islpy'. Skipping.
git+https://github.com/inducer/pyopencl.git@v2020.2.2-62-gbf471e3#egg=pyopencl
git+https://github.com/inducer/loopy.git@f807a864#egg=loo
git+https://github.com/inducer/dagrt.git@00afbb0#egg=dagrt
git+https://github.com/inducer/leap.git@f1b5a3e#egg=leap
git+https://github.com/inducer/modepy.git@d8f8824#egg=modepy
git+https://github.com/inducer/meshmode.git@c0cb6d6#egg=meshmode
git+https://github.com/inducer/grudge.git@4a19f15#egg=grudge
Warning: missing module 'f2py'. Skipping.
**Created file 'requirements.txt.G6t7kG'. Install it with 'pip install -r requirements.txt.G6t7kG'.

$ cat requirements.txt.G6t7kG
# requirements.txt created by version.sh
# Date: Thu Oct 15 23:39:49 CDT 2020
git+https://github.com/inducer/pymbolic.git@v2020.1-44-g3ff0732#egg=pymbolic
git+https://github.com/inducer/pyopencl.git@v2020.2.2-62-gbf471e3#egg=pyopencl
git+https://github.com/inducer/loopy.git@f807a864#egg=loo
git+https://github.com/inducer/dagrt.git@00afbb0#egg=dagrt
git+https://github.com/inducer/leap.git@f1b5a3e#egg=leap
git+https://github.com/inducer/modepy.git@d8f8824#egg=modepy
git+https://github.com/inducer/meshmode.git@c0cb6d6#egg=meshmode

[matthiasdiener]

~TODO: add creation of conda env file~

Edit: Separate issue: #84.

[matthiasdiener]

Ready for review