Fix leading zero problem in YAML front matter

[joeyaiello]

Apparently you need to put single quotes around numbers with leading zeros in YAML, and many of our RFC numbers are probably wrong because of this. We should fix it.

[JamesWTruher]

Filename

RFC0003-Lexical-Strict-Mode.md
RFC0001-Mutual-Exclusion-Parameters-and-Properties.md
RFC0053-PowerShell-IoT-Module.md
RFC0005-Typed-Interprocess-communication.md
RFC0006-Universal-Parsing-and-Piping.md
RFC0007-Weak-Aliases.md
RFC0009-Glob-for-Native-Tools.md
RFC0011-Dot-Referencing-With-Static-Integers.md
RFC0002-Generalized-Splatting.md
RFC0018-Get-StringHash.md
RFC0004-PowerShell-Module-Versioning.md
RFC0049-PSModulePath.md
RFC0050-Importing-Windows-PowerShell-modules-in-PowerShell-Core.md
RFC0051-Null-conditional-operators.md
RFC0052-Notification-On-Version-Update.md