Add helper for lowercase list of strings
Add case-insensitive flag to `MDBIndex`
Test DNS case-insensitivity
Always lowercase incoming DNS query
Remove DC case-insensitive check from node test
Lowercase index key and lookup value if flag is set
Make service index case-insensitive
Make service tag filter case-insensitive
Change order of fixtures
Don't override `ServiceTags`
Short doc note about DNS case-insensitivity
Update CHANGELOG.md
Merge pull request #224 from hashicorp/f-case-insensitivity

DNS case-insensitivity