Clarify differentiate() coordinate values.
Add skip_data for tests that require it.
Merge pull request #1263 from QuLogic/tests-skip_data

Add skip_data for tests that require it.
Merge pull request #1253 from rhattersley/differentiate-docs

Clarify differentiate() coordinate values.
fixed tolerance bug in intersection
review actions
Explicitly set version of gribapi
BUG: Fixed varname setting in aux con.
Merge pull request #1283 from cpelley/corrected_netcdf_varname

BUG: Fixed varname setting in aux con.
Merge pull request #1282 from dkillick/explicit_gribapi_ver

Explicitly set version of gribapi in .travis.yml
Merge pull request #1271 from esc24/intersectionbug17

Fixed tolerance bug in intersection
Merge remote-tracking branch 'upstream/v1.7.x' into megred_17x_changes

Conflicts:
	lib/iris/tests/unit/fileformats/pyke_rules/compiled_krb/fc_rules_cf_fc/test_build_dimension_coordinate.py
Merge pull request #1286 from cpelley/megred_17x_changes

Merged 1.7.x changes to master