Warmup steps allows values <1 as percentage of total

[efhosci]

Changes "warmup steps" parameter from int to float. For input values >1 it behaves the same way as it did previously, warmup steps / gradient steps. For values between 0-1, it changes to warmup steps * total steps (total steps already compensates for gradient accumulation). Any other values will be set to zero. Also modified mouseover text to reflect that change.

Some examples of behavior, tested with total steps 100. Also verified warmup behavior correctly works for different gradient accumulation values, though I did come across an issue related to changing that value while training is running (see issue #557):

• Warmup set to 50 = 50 steps of warmup, 50 steps of scheduler
• Warmup set to 0.4 = 40 steps of warmup, 60 steps of scheduler
• Warmup set to -0.3 = 0 steps of warmup, 100 steps of scheduler
• Warmup set to -20 = 0 steps of warmup, 100 steps of scheduler
• Warmup set to 1 = 100 steps of warmup, 0 steps of scheduler

[O-J1]

@efhosci Did you mean to close this?

[efhosci]

Sorry about that, I split the changes i just submitted into a different branch.