Update data.r

This variable is never used, so I believe it can be safely removed
export sample_n/frac methods for grouped_df
Update group-by.r
Merge pull request #472 from ijlyttle/patch-1

Update group-by.r
Re-document
Merge pull request #468 from alyst/sample_n_grouped_df

Export sample_n/frac methods for grouped_df. Closes #405.
Update news
Remove extraneous classes in copy_to.
Closes #469
Merge pull request #466 from jimhester/patch-1

Update data.r
Coerce n to integer. Closes #407
Throw error in select for bad indexes.
Closes #348
Implement distinct for ungrouped tbls
Add grouped methods for distinct
Re-document
Add sql_select method for bigquery.
Fix order_by behaviour. Improve bq windowing support
More join types in join_sql
First pass at joins with diff x and y vars
Add join tests.
Move by length check into common_by
Do not show progress bar if not interactive or knitr in progress

Checking a NULL value for true results in an error

The previous commit correctly did not print the progress bar when
knitting, but it also threw an error when not knitting, this commit
fixes the issue in both cases

Add note to news

Correct issue number

Move progress bar interactive use to latest news block

Checking a NULL value for true results in an error

The previous commit correctly did not print the progress bar when
knitting, but it also threw an error when not knitting, this commit
fixes the issue in both cases

Add note to news

Correct issue number