Add option to ignore major version inconsistencies

[bmish]

It might be easier to only consider patch/minor version inconsistencies first since these shouldn't have breaking changes. One may want to consider/fix major version inconsistencies separately.

Possible APIs:

• --ignore-semver major -- ignore anything with major version inconsistency
• --semver minor,patch -- only consider minor / patch version inconsistencies
• --ignore-range -- ignore range type inconsistencies (e.g. tilde vs caret)
• --ignore-range caret,tilde -- ignore anything with a caret or tilde range