Update version.txt

Release 1.2.7

Merge pull request #276 from NASA-IMPACT/dev

Created new version for citation file and README updates

Merge pull request #271 from NASA-IMPACT/dev

Updates to README and umm-g schema file

Merge pull request #268 from NASA-IMPACT/dev

Minor fixes and additional checks:
- Updated UMM-C schema file
- Added science_keywords_presence_check
- Added DOI authority presence check for echo-c and umm-c
- Adjusted output message for url_check
- Added orbit fields to rule_mapping for spatial_extent_fulfillment_check
- Resolved ISO standard type in check_messages

Merge pull request #251 from NASA-IMPACT/dev

Updates: Adding Checks and Resolving Inconsistencies

Fix minor bugs

- stray newlines in GCMD keyword files
- reading xml metadata for fields with attributes didn't get the expected output
- missing field in rule_mapping

Merge pull request #224 from NASA-IMPACT/develop

Updates from Regression Testing and Minor Fixes

Merge pull request #202 from NASA-IMPACT/dev

Add support for formats (`echo-g`, `umm-g`, `umm-c`) and custom cmr host

Merge pull request #173 from NASA-IMPACT/ench-version_update

Ench version update