[Feature Request] Partial MD5 value

[jheddings]

It would be great if there was a way to use part of the MD5 hash, rather than the entire string. This could be useful for generating a shorter unique name, for example:

• Use the first 2 bytes from the MD5 hash as path elements: {md5[0]}/{md5[1]}/{date}
• Use a slice of the MD5 hash similar to git commit ID: {date}-{md5[0:7]}

Another cool feature would be to filter the MD5 has to modify the letter case:

• Make the MD5 hash lower case: {md5|lower}

Thanks for a great plugin!

[simexce]

I implemented the ${v[:]} format, you can try it out. #186