I'm trying to update Bioconductor, i've got R 3.3.1 installed but when i run biocLite() I get this message

BioC_mirror: https://bioconductor.org
Using Bioconductor 3.4 (BiocInstaller 1.24.0), R 3.3.1 (2016-06-21).
installation path not writeable, unable to update packages: BH, cluster,
  codetools, colorspace, curl, digest, evaluate, forcats, foreign, ggplot2,
  hms, jsonlite, knitr, lattice, Matrix, mgcv, nlme, openssl, psych, R6, Rcpp,
  reshape2, rmarkdown, scales, selectr, stringi, survival, tidyr, tidyverse,
  xml2, yaml

I'm on Mac OS 10.10.1

Anyone can tell me what's up?

The error is 'installation path not writeable', which means that you don't have permissions to modify files and or directories in your library path. The main way this sort of thing happens is when you install R as a user with more permissions, and then run R as a user with lower permissions.

Canonical examples are installing R under sudo on *nix OSes (which includes MacOS), or installing R as administrator on Windows. Running R as a 'regular' user with lower privileges and trying to install packages in a privileged directory will give an error saying the path isn't writeable.