Edited tutorial documentation

[pepak13]

The documented output from signac schema for the ideal gas tutorial gives the incorrect pressure range 0 to 10. From the init script, the result is 0 to 9 and the change correctly shows that.

Description

Changed the beginning of the tutorial documentation to correctly reflect the output of signac schema.

Motivation and Context

Fixes issue: #72

Checklist:

• I am familiar with the Contributing Guidelines.
• I agree with the terms of the Contributor Agreement.
• My code follows the code style guideline of this project.

[vyasr]

@lyrivera since this PR is pretty trivial I'm going to go ahead and merge without your approval. Let me know if you do take a look and if you find any problems.

@pepak13 thanks for the contribution!