update minimal R version due to proxy package requirements

[MarcinKosinski]

I can't use the package createJSON function on R 3.3.1 due to the fact proxy package needs R to be equal or greater thatn 3.3.2 https://cran.r-project.org/web/packages/proxy/index.html

> json <- createJSON(
+       phi = phi, 
+       theta = theta, 
+       doc.length = fit$statistics$doc.length, 
+       vocab = fit$statistics$vocab, 
+       term.frequency = fit$statistics$term.frequency
+     )
Error in loadNamespace(name) : there is no package called ‘proxy’
> install.packages('proxy')
Warning in install.packages :
  package ‘proxy’ is not available (for R version 3.3.1)
> sessionInfo()
R version 3.3.1 (2016-06-21)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

locale:
[1] LC_COLLATE=Polish_Poland.1250  LC_CTYPE=Polish_Poland.1250   
[3] LC_MONETARY=Polish_Poland.1250 LC_NUMERIC=C                  
[5] LC_TIME=Polish_Poland.1250    

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
 [1] LDAvis_0.3.2        lda_1.4.2           pbapply_1.3-2       koRpus_0.10-2      
 [5] data.table_1.9.6    tm_0.7-1            NLP_0.1-10          stringi_1.1.5      
 [9] NbClust_3.0         cluster_2.0.5       factoextra_1.0.4    foreach_1.4.3      
[13] openxlsx_3.0.0      networkD3_0.3       VennDiagram_1.6.17  futile.logger_1.4.3
[17] Boruta_5.2.0        ranger_0.6.0        scales_0.4.1        ggmosaic_0.1.2     
[21] productplots_0.1.1  corrplot_0.77       stringr_1.2.0       magrittr_1.5       
[25] dplyr_0.5.0         purrr_0.2.2         readr_1.0.0         tidyr_0.6.1        
[29] tibble_1.3.0        tidyverse_1.0.0     readxl_0.1.1        haven_1.0.0        
[33] plyr_1.8.4          tables_0.8          Hmisc_4.0-2         ggplot2_2.2.1      
[37] Formula_1.2-1       survival_2.40-1     lattice_0.20-34    

loaded via a namespace (and not attached):
 [1] ggrepel_0.6.5        Rcpp_0.12.8          assertthat_0.2.0     digest_0.6.12       
 [5] slam_0.1-40          R6_2.2.0             chron_2.3-47         futile.options_1.0.0
 [9] backports_1.0.4      acepack_1.4.1        httr_1.2.1           lazyeval_0.2.0      
[13] rpart_4.1-10         Matrix_1.2-7.1       checkmate_1.8.2      labeling_0.3        
[17] devtools_1.12.0      splines_3.3.1        foreign_0.8-67       htmlwidgets_0.8     
[21] igraph_1.0.1         munsell_0.4.3        compiler_3.3.1       base64enc_0.1-3     
[25] htmltools_0.3.5      nnet_7.3-12          gridExtra_2.2.1      htmlTable_1.9       
[29] codetools_0.2-15     viridisLite_0.1.3    withr_1.0.2          jsonlite_1.4        
[33] gtable_0.2.0         DBI_0.5-1            reshape2_1.4.2       latticeExtra_0.6-28 
[37] lambda.r_1.1.9       RColorBrewer_1.1-2   iterators_1.0.8      tools_3.3.1         
[41] parallel_3.3.1       colorspace_1.3-1     memoise_1.0.0        plotly_4.5.6        
[45] knitr_1.15   

[cpsievert]

Thanks!