Fix an issue where numbers were being highlighted as properties

Improves regex for swiftMethod and swiftProperties to expect a non-digit
following a period, as swift does not allow methods/funcs starting with
a digit.

Resolves #100

example/example.swift

@@ -49,6 +49,7 @@ if foo {
 5 // int
 
 5.5 // float
+45.4
 5e-2
 5E2
 5.5E-2

syntax/swift.vim

@@ -90,8 +90,8 @@ syntax match swiftOperator "\v\>"
 syntax match swiftOperator "\v\?\?"
 
 " Methods/Functions/Properties
-syntax match swiftMethod "\(\.\)\@<=\w\+\((\)\@="
-syntax match swiftProperty "\(\.\)\@<=\<\w\+\>(\@!"
+syntax match swiftMethod "\.\@<=\<\D\w*\>\ze("
+syntax match swiftProperty "\.\@<=\<\D\w*\>(\@!"
 
 " Swift closure arguments
 syntax match swiftClosureArgument "\$\d\+\(\.\d\+\)\?"