Fix for numeric series names

[MHewison]

New Pull Request

Exporting charts which have used integers as series name causes an error. This PR is to simple coerce the passed series title into a string for export purposes.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[junedchhipa]

Please remove the /dist directory as it is only required when a new version is built.