fixes node-version of isInt() to work as stated in README

node-version of isInt() did let zeropadded numbers pass. Updated node-versions code to the working code of the browser-version.
changes toLowercase()/toUppercase() to let more than a-z and 0-9 pass

isLowercase()/isUppercase() failed on whitespace, punctuation marks and non-ascii letters because of a too strict regex check. Now comparing given string to the result of native toLowerCase()/toUpperCase() functions.
fixes isDivisibleBy() to fail on alphabetic strings
adds isDivisibleBy() to browser-version
changes .contains() to fail on empty strings
changes isIP to rely on isIPv4() and isIPv6()
adds isIPv4() and isIPv6() to browser-version
adds isIPv4() and isIPv6() to README.md
adds is(), not() and isFloat() to node-version
adds isUUIDv3(), isUUIDv4() to match with isIP() methods
Merge pull request #172 from tbasse/fix/isIP

Add isIPv4() and isIPv6() to browser-version and README.md
Merge pull request #170 from tbasse/fix/isDivisible

Fixes isDivisibleBy() and adds it to the browser-version
Merge pull request #169 from tbasse/fix/isInt

fixes node-version of isInt() to work as stated in README
Merge pull request #171 from tbasse/fix/isLowerUpperCase

toLowercase() and toUppercase() fail on foreign characters
Merge pull request #174 from tbasse/fix/addMissing

Add is(), not() and isFloat() to node-version
Merge pull request #175 from tbasse/fix/isUUID

Add isUUIDv3(), isUUIDv4() to match with isIP methods
Merge pull request #173 from tbasse/fix/contains

contains() passes with empty strings
0.5.0
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