Remove invalid characters in log stream and log group names.

[davidnewhall]

Issue #, if available: #103

Description of changes:

• Adds sanitize functions for both of logs stream names and log group names.
• Truncates group or stream names over the maximum of 512 characters.
• Adds test for both of these ^^^
• Moves the fasttemplate.Template creation and error into the startup routine instead of the log line routine.
  • This allows invalid templates defined in the config file to throw errors sooner.
  • Speeds up the log processing pipeline a tiny bit.
• The existing template parsing procedures were modified to take different inputs:
  • The new sanitize functions as a direct interface.
  • The template input string was modified to become a fasttemplate.Template input.
• Adds t.Parallel() to two existing tests to speed them up.

To go along with this, I'm working on another PR for #99.

EDIT: I think I've worked my way through all my concerns and made this as fast as possible. It's now ready for review. Recommend a merge squash when we get there.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[PettitWesley]

@davidnewhall Thanks!

[PettitWesley]

@davidnewhall Thanks!