Fix sha-256 hash name in example
Remove trailing equal signs from the sha-512 examples

As per step 4 of "Apply algorithm to resource", the base64 encoding
of hashes are not supposed to have trailing equal signs.
Update the digest definition to remove trailing equal signs
Remove unnecessary step in "Get the strongest metadata from set"

The invalid ni URLs are already filtered out in the "Parse
metadata" algorithm.
Remove unnecessary step "Does resource match metadataList"

This step is not needed because the "Get the strongest metadata
from set" algorithm would only return an empty string if the
"Parse metadata" return an empty set. If that were the case, we
would never get to this step and instead would exit the algorithm
at Step 4.
Remove second unnecessary step in "Does resource match metadataList"

As of 7d0c06e7d73d2d80a570c97ccc517ad084f74bfc, the "Apply
algorithm to resource" algorithm never returns null.
Label the three components of metadata

Include the labels used in the reference algorithms to refer to
these three components of the integrity metadata.
Merge pull request #78 from josh/fix-hash-example

Fix sha-256 hash name in example
Merge pull request #89 from fmarier/remove-equal-signs

Remove trailing equal signs from the sha-512 examples
Merge pull request #96 from fmarier/remove-more-unnecessary-steps

Remove more unnecessary steps
Merge pull request #97 from fmarier/label-metadata-components

Label the three components of metadata
POWER: Implementation considerations.