use downcase string for extname
determine image with downcase extname
Added to vendor.yml the following dependencies related to automake and autoconf:
- (^|/)configure
- (^|/)configure.ac
- (^|/)config.guess
- (^|/)config.sub

Before changing:
[herbert@vps11071 linguist]$ bundle exec linguist ../atmi++/
75%  Shell
15%  C++
10%  C
0%   Perl

After changing:
54%  C++
37%  C
9%   Shell
0%   Perl
Merge remote-tracking branch 'upstream/master'
Add a misclassified Prolog file

This Prolog file was misclassified as Perl.  I assume linguist
was confused because the file has many comments.  Nevertheless,
there are plenty of Prolog-distinguishing tokens such as `:-`,
`module`, `%%`, capitalized variables names, `foo/2`, etc.
Merge branch 'master' of https://github.com/github/linguist
Update lib/linguist/languages.yml

Add DOT language: http://www.graphviz.org/content/dot-language
Update lib/linguist/languages.yml

Add .gv (GraphViz) file extension to DOT language.
Samples for Processing language, changes to languages.yml
New language: XProc - an XML Pipeline language (W3C)
added XML lexer
More Forth samples.
Added matlab code samples.
All of these code samples currently are mis-identified in my repositories. I'm
donating them to the cause.
Put Processing language into alphabetical order, re: #383
Update lib/linguist/languages.yml

Change sort order
Update lib/linguist/languages.yml

Set lexer to Text only for DOT. This hopefully fixed the failure on Travis.
Added one more file
Add ABAP
Add support for the Logos language.
Update samples.json to include Logos.