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.
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 1049

Conflicts:
	lib/linguist/samples.json
Merge pull request #1098 from github/1049-update

1049 update