Bug fixes and performance improvement

New Features:

• Add legend.hide option - #731
• Add axis.y.inner and axis.y2.inner options - #742

Bug Fixes:

• Fix point.show not to hide scatter plot - #732
• Fix class suffix for back slash - #734
• Fix data.values API - #736
• Fix bug for zoom.rescale - #738
• Fix empty data when timeseries - #737

Performance Improvement:

• Refactor tick char size calculation - #730
• Cache legend item text rect - #730
• Cache tick text size - #730