Features: DMS format for graticule labels,

[kordaniel]

Proposal for a few changes to this fine repository.

Changes:

• Add option to render graticule lines degrees in DMS form, keep DD as default.
• Add option to render graticule lines labels with a larger font (css 1.25em).
• Add lineStyle to AutoGraticuleOptions interface, refactor lineStyle object of AutoGraticule into options.
• Refactor AutoGraticule constructor to override default options for all options passed in.
• Bump version 2.0.0 -> 2.1.0.

These changes enables the end user of the library to pass in an options object that will overwrite the defaults for all the provided fields, while default options are used for the rest of options.