flow converts memory directive to float

[atravitz]

Description

flow passes the memory directive to SLURM as a float, which at least for greatlakes is invalid.

To reproduce

Passing memory=8 results in a SLURM script containing --mem=8.0G

Error output

sbatch: error: Invalid --mem specification

System configuration

Please complete the following information:

• Operating System [e.g. macOS]:
• Version of Python [e.g. 3.7]:
• Version of signac [e.g. 1.0]:
• Version of signac-flow: 0.13.0

Or copy & paste the output of: python -c 'import platform; print(platform.platform()); import sys; print(sys.version); import signac; print(signac.__version__); import flow; print(flow.__version__)'