title: Error with select function from dplyr
body: <p>When I use the select function from dplyr, it doesn't work and gives me an error stating that the column names that I want to select are unused arguments. However, if I specify dplyr before the function call like s: "dplyr::select" then it works as normal:</p>
  
  <p>Here is a sample df:</p>
  
  <pre><code> sampledf &lt;- structure(list(CRN = c(5497L, 6515L, 7248L, 36956L, 37021L), 
          varA = structure(c(2L, 2L, 2L, 2L, 2L), .Label = c("A", 
          "B"), class = "factor"), varB = c(NA_integer_, NA_integer_, 
          NA_integer_, NA_integer_, NA_integer_), VarC = c(NA, NA, 
          NA, NA, 2L), varD = c(NA_integer_, NA_integer_, 
          NA_integer_, NA_integer_, NA_integer_), varE = c(1L, 1L, 4L, NA, NA)), .Names = c("CRN", 
          "varA", "varB", "varC", "varD", "varE"), row.names = c(NA, 5L), class = "data.frame")
  </code></pre>
  
  <p>this produces the error:</p>
  
  <pre><code> sample_error &lt;- select(sampledf, varA)
  </code></pre>
  
  <blockquote>
    <p>Error in select(sampledf, varA) : unused argument (varA)</p>
  </blockquote>
  
  <p>and this works:</p>
  
  <pre><code> sample_working &lt;- dplyr::select(sampledf, varA)
  
   version
  </code></pre>
  
  <blockquote>
    <p>version
                   _<br>
    platform       x86_64-w64-mingw32<br>
    arch           x86_64<br>
    os             mingw32<br>
    system         x86_64, mingw32<br>
    status<br>
    major          3<br>
    minor          4.0<br>
    year           2017<br>
    month          04<br>
    day            21<br>
    svn rev        72570<br>
    language       R<br>
    version.string R version 3.4.0 (2017-04-21)
    nickname       You Stupid Darkness        </p>
  </blockquote>
  
  <p>And here is the session info:</p>
  
  <pre><code>sessionInfo()
  </code></pre>
  
  <blockquote>
    <p>R version 3.4.0 (2017-04-21)
    Platform: x86_64-w64-mingw32/x64 (64-bit)
    Running under: Windows >= 8 x64 (build 9200)</p>
    
    <p>Matrix products: default</p>
    
    <p>locale:
    [1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United States.1252    LC_MONETARY=English_United States.1252
    [4] LC_NUMERIC=C                           LC_TIME=English_United States.1252    </p>
    
    <p>attached base packages:
    [1] stats     graphics  grDevices utils     datasets  methods   base     </p>
    
    <p>other attached packages:
     [1] readxl_1.0.0    bindrcpp_0.2    doBy_4.5-15     reshape2_1.4.2  ltm_1.0-0       > polycor_0.7-9   msm_1.6.4<br>
     [8] MASS_7.3-47     glmnet_2.0-10   foreach_1.4.3   Matrix_1.2-9    caret_6.0-76    lattice_0.20-35 dplyr_0.7.2<br>
    [15] purrr_0.2.3     readr_1.1.1     tidyr_0.6.3     tibble_1.3.3    > > > > > > ggplot2_2.2.1   tidyverse_1.1.1 openxlsx_4.0.17</p>
    
    <p>loaded via a namespace (and not attached):
     [1] Rcpp_0.12.11       lubridate_1.6.0    mvtnorm_1.0-6      assertthat_0.2.0   > psych_1.7.5        R6_2.2.2<br>
     [7] cellranger_1.1.0   plyr_1.8.4         MatrixModels_0.4-1 stats4_3.4.0       > httr_1.3.1         rlang_0.1.1<br>
    [13] lazyeval_0.2.0     minqa_1.2.4        SparseM_1.77       car_2.1-4          > nloptr_1.0.4       labeling_0.3<br>
    [19] splines_3.4.0      lme4_1.1-13        stringr_1.2.0      foreign_0.8-67     munsell_0.4.3      broom_0.4.2<br>
    [25] compiler_3.4.0     modelr_0.1.1       pkgconfig_2.0.1    mnormt_1.5-5       mgcv_1.8-17        nnet_7.3-12<br>
    [31] expm_0.999-2       codetools_0.2-15   ModelMetrics_1.1.0 grid_3.4.0         nlme_3.1-131       jsonlite_1.5<br>
    [37] gtable_0.2.0       magrittr_1.5       scales_0.4.1       stringi_1.1.5      xml2_1.1.1         iterators_1.0.8<br>
    [43] tools_3.4.0        forcats_0.2.0      glue_1.1.0         hms_0.3            survival_2.41-3    parallel_3.4.0<br>
    [49] pbkrtest_0.4-7     colorspace_1.3-2   rvest_0.3.2        bindr_0.1          haven_1.1.0        quantreg_5.33 </p>
  </blockquote>