Add the Mercury language to linguist

lib/linguist/languages.yml:
    Add the declaration for the language.

samples/Mercury:
    Add samples for the classifier as Mercury shares it's filename extension
    with several other languages.
MATLAB uses .m files not .matlab.
Reverted to the .matlab extension and added .m as another extension.
Added .h as an Objective-C file type
Changed the order of the Objective-C files.
Add support for the GAP language
Update languages.yml

Detect Inno Setup installer scripts (http://www.jrsoftware.org/isinfo.php)
Update vendor.yml

extend the vendor/ exclusion to handle vendors/

Some projects use this folder to store external libaries (eg https://github.com/Elgg/Elgg)
Add the Mercury language to linguist

lib/linguist/languages.yml:
    Add the declaration for the language.

samples/Mercury:
    Add samples for the classifier as Mercury shares it's filename extension
    with several other languages.
fixing merge conflict in vendor.yml
changed mercury extension to .mercury, to avoid conflict with Obj-C
Included store.m in Mercury/samples, now 100% coverage in Mercury library/ and compiler/
added Mercury/ to 'vendor' directory
added .moo (parser definitions) to Mercury extension list
Merge remote-tracking branch 'upstream/master' into mercury-noconflict
Merge branch 'master' into 989

Conflicts:
	lib/linguist/languages.yml
Merge pull request #1096 from github/989-update

989 update
Merge branch 'master' into 1046

Conflicts:
	lib/linguist/languages.yml
	lib/linguist/samples.json
Merge pull request #1097 from github/1046-update

1046 update
Merge branch 'master' into 1049

Conflicts:
	lib/linguist/samples.json