Bibliography .bib encoding utf8 (french) accents

You should use the modern replacement for bibtex: biblatex with its biber backend. It is fully unicode capable.

If you want to take it one more step further, you might also want to switch to a native unicode-enginge: xelatex or lualatex. You just have to change a few packages in the preamble. The combination of \usepackage[utf8]{inputenc} and \usepackage[T1]{fontenc} has to be replaced by \usepackage{fontspec}.

This package takes care of font and input encoding. All you need are utf8 encoded source files. You can also use every truetype or opentype font.

For language support polyglossia should be preferred to babel.

Here is an example that works both with lualatex and xelatex:

\documentclass{scrartcl}

\begin{filecontents}{references.bib}
   @ARTICLE{test,
     TITLE = {à è ê á é},
     JOURNAL = {des accents},
     YEAR = {2015},
   }
\end{filecontents}

\usepackage{fontspec}
\usepackage{polyglossia}
\setmainlanguage{french}

\usepackage[backend=biber]{biblatex}
\addbibresource{build/references.bib}

\begin{document}
  \cite{test}
  \printbibliography
\end{document}

Compile e.g. with lualatex test.tex, biber test.bcf, lualatex test.tex, lualatex test.tex.

If you want to still use pdflatex, it would look like this:

\documentclass{scrartcl}

\begin{filecontents}{references.bib}
   @ARTICLE{test,
     TITLE = {à è ê á é},
     JOURNAL = {des accents},
     YEAR = {2015},
   }
\end{filecontents}

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[french]{babel}

\usepackage[backend=biber]{biblatex}
\addbibresource{build/references.bib}

\begin{document}
  \cite{test}
  \printbibliography
\end{document}

Compile with pdflatex test.tex, biber test.bcf, pdflatex test.tex, pdflatex test.tex