Utilities for parsing numbers and string versus seq[char]

[schneiderfelipe]

Implement the relevant parsers from Text.Megaparsec.Char.Lexer.

By the way, the following does not work

import parseutils
import microparsec
let p = many1(digit).map(parseInt)
echo p.parse("1234") + 1  # should be 1235

/home/schneider/Dropbox/microparsec/examples/asdf.nim(3, 21) Error: type mismatch: got <Parser[seq[char]],
proc (s: string, number: var int, start: int): int{.noSideEffect, gcsafe, locks: 0.}>
but expected one of: 
func map[S, T](parser: Parser[S]; f: S -> T): Parser[T]
  first type mismatch at position: 2
  required type for f: proc (i0: S): T{.closure.}
  but expression 'parseInt' is of type: proc (s: string, number: var int, start: int): int{.noSideEffect,
gcsafe, locks: 0.}

expression: map(
  liftA2(proc (x: T; xs: seq[T]): auto = result = x & xs, digit, many digit),
    parseInt)

which is related to #6.