Preserve the fractional part of match number, for 'category(srm=1)'

The contest category renderer, applied to ${Contest;category(srm=1)},
drops the fractional part of the SRM match number. Consequently, for
example, the rendered result for SRM 600.5 becomes "SRM 600".

The option 'srm=1' is usually used with the special aim of separating
each round differently (similar but slightly different from ${Contest.Name}).
Therefore the case should be handled specially.
Merge pull request #138 from wookayin/fix/srm-category

Preserve the fractional part of match number, for 'category(srm=1)'