Build .beam location from scratch on mix compile.elixir

Signed-off-by: José Valim <jose.valim@plataformatec.com.br>
 Add OTP 17.3 to run on Travis CI

Signed-off-by: José Valim <jose.valim@plataformatec.com.br>
set null prompt function in dumbterm mode

Signed-off-by: José Valim <jose.valim@plataformatec.com.br>
Merge pull request #2819 from benjamintanweihao/patch-3

Fix missing concatenation operator.

Signed-off-by: José Valim <jose.valim@plataformatec.com.br>
No longer inline binary expressions in EEx

String.Chars is now always inlined by the compiler.

Closes #2815

Signed-off-by: José Valim <jose.valim@plataformatec.com.br>
Update CHANGELOG