Move lexer predicates to the right hand side

[JD557]

Moves the lexer predicates to the right side of the rule, as suggested by: https://github.com/antlr/antlr4/blob/master/doc/predicates.md#predicates-in-lexer-rules

Addresses #93 (not sure if this can be considered fixed yet).

Using @mbaumbach benchmarks:

Old Version

Parsing small
Parse time (attempt: 1): 352
Parse time (attempt: 2): 2
Parse time (attempt: 3): 2
Parse time (attempt: 4): 2
Parse time (attempt: 5): 1
Parse time (attempt: 6): 2
Parse time (attempt: 7): 1
Parse time (attempt: 8): 2
Parse time (attempt: 9): 2
Parse time (attempt: 10): 1
Parsing medium
Parse time (attempt: 1): 99
Parse time (attempt: 2): 96
Parse time (attempt: 3): 73
Parse time (attempt: 4): 55
Parse time (attempt: 5): 77
Parse time (attempt: 6): 58
Parse time (attempt: 7): 54
Parse time (attempt: 8): 46
Parse time (attempt: 9): 35
Parse time (attempt: 10): 45
Parsing large
Parse time (attempt: 1): 120
Parse time (attempt: 2): 83
Parse time (attempt: 3): 127
Parse time (attempt: 4): 100
Parse time (attempt: 5): 86
Parse time (attempt: 6): 93
Parse time (attempt: 7): 128
Parse time (attempt: 8): 164
Parse time (attempt: 9): 78
Parse time (attempt: 10): 74

New Version

Parsing small
Parse time (attempt: 1): 311
Parse time (attempt: 2): 2
Parse time (attempt: 3): 1
Parse time (attempt: 4): 2
Parse time (attempt: 5): 0
Parse time (attempt: 6): 0
Parse time (attempt: 7): 0
Parse time (attempt: 8): 1
Parse time (attempt: 9): 0
Parse time (attempt: 10): 0
Parsing medium
Parse time (attempt: 1): 27
Parse time (attempt: 2): 14
Parse time (attempt: 3): 12
Parse time (attempt: 4): 10
Parse time (attempt: 5): 9
Parse time (attempt: 6): 8
Parse time (attempt: 7): 7
Parse time (attempt: 8): 7
Parse time (attempt: 9): 7
Parse time (attempt: 10): 7
Parsing large
Parse time (attempt: 1): 31
Parse time (attempt: 2): 35
Parse time (attempt: 3): 38
Parse time (attempt: 4): 32
Parse time (attempt: 5): 24
Parse time (attempt: 6): 26
Parse time (attempt: 7): 30
Parse time (attempt: 8): 30
Parse time (attempt: 9): 16
Parse time (attempt: 10): 21

[bkiers]

Wasn't aware of that. Nice work @JD557!