fix 0.5 deprecation in test script

Author: stevengj

test/runtests.jl

@@ -8,7 +8,7 @@ tst1u = Compat.UTF8String(tst1)
 @test L"\alpha^2" == "\$\\alpha^2\$"
 @test stringmime("text/latex", tst1) == tst1u
 buf = IOBuffer()
-writemime(buf, "text/latex", tst1)
+@compat show(buf, "text/latex", tst1)
 @test takebuf_string(buf) == tst1u
 @test latexstring(tst1u) == tst1 == LaTeXString(tst1u)